Slaven Bilic and his charges were made to pay for some lacklustre work at home, though, as they were beaten by a solitary goal from frontman Filipe Teixeira, who sent the Romanian champions through with a 2-1 aggregate win.
Relive all of the action with our minute-by-minute updates below.
6.46pmTonight's winners will be heading through into the group stages of the tournament and the Hammers will be aiming to get the better of the Romanian champions, who dumped the Irons out of the Europa during the third round of qualifying last campaign.
6.47pmSlaven Bilic and his charges are arguably much improved since then and they will be confident of earning progress thanks to an away goal notched in the sides's 1-1 draw in the first leg last week.
6.50pmMark Noble was the hero last time out with a penalty on Romanian soil, but the Hammers will feel irritated after allowing Denis Alibec's late equaliser to bring the scores level at 1-1. What matters, though, is that Bilic and company now have an away goal in the bag. All they need to do tonight is win at home and they'll be through. A goalless draw would also do as well for the Hammers.
6.58pmSo Bilic has made a number of changes from his West Ham side that beat Bournemouth in the Premier League at the weekend. The major change is that Noble has dropped out of the squad, while newcomer Havard Nordtveit gets a chance just in front of the defence. The Hammers are to play five across the middle, which is also inclusive of Gokhan Tore on the right and Michail Antonio on the left. Pedro Obiang and Cheikhou Kouyate are to feature in the centre with lone striker Jonathan Calleri operating up top.
7.05pmAntonio will be delighted that he's got another chance to feature on the wing other than in the full-back position this evening. Following his winner at the week, Antonio became the scorer of the club's first league goal at the London Stadium, while he also earned their last-ever goal at Upton Park last campaign.
7.08pmThat midfield five looks particularly intriguing this evening and the Hammers have pace in abundance in that four being played just in front of Nordtveit. You might have argued that the Hammers were a little too slow in their build-up play last week and Bilic will be looking for some more incision tonight. The atmosphere was a touch restrained against Tournament at the weekend and the West Ham players will be hoping to give their fans something to get excited about this evening.
7.10pmDespite claiming the Romain top-flight title last year, Astra have found things difficult domestically this term and have perhaps been playing better in Europe. At the moment, the club have just four points from their opening five matches and lost 5-1 to CFR Cluj over the weekend.
7.12pmIt appears as though both Payet and Lanzini are being saved for the weekend as they do not appear in the squad tonight. Having looked at the starting XI, though, you would still have to back West Ham having enough to gain qualification.
7.15pmRegardless of West Ham's away goal, Astra boss Marius Sumudica believes that his side can still turn this around having already attained positive results against the Hammers in the past. Here's what he told the official West Ham website recently: "Obviously it helps that we're unbeaten in three games against West Ham, but on Thursday they will be the favourites playing on home soil with all their fans behind them.They have a great manager in Slaven Bilic and a great team, but we will try our best to win."
7.17pmBillie himself, though has also admitted that although the away goal gives his time a slight advantage, they will not be treating this game any differently. Here's what he said prior to the contest, according to BBC Sport: "We are not going to protect the away goal. It gives you an advantage but you cannot hang on for 90 minutes. We will play a normal game."
7.19pmThe last time these two sides met prior to this tie, West Ham found themselves on the losing end of an aggregate result that saw Astana progress beyond them in the qualifying stages. The Romanian side drew at the Boleyn Ground before claiming a 2-1 victory back on home soil.
7.20pmThe omens tend to bode well when West Ham's Byram is on the bench. A little fact for you this evening: the full-back has never lost a home fixture for the Hammers.
7.22pmThis game's importance is magnified tenfold given the club's current situation with the stadium. To merit an architectural achievement of this magnitude, surely the Irons need to be playing some sort of European football this campaign? They're potentially just 90 minutes away from achieving that!
7.24pmHere's a quick clip of some footage inside the London Stadium, where substitute keeper Adrian is showing off some skills. The weather in the English capital is a little bit cooler than the scoring temperatures yesterday, but things are a touch muggy out there tonight:
7.27pmOne slight concern for the Hammers tonight might just be their bench... They have Enner Valencia, James Collins and Adrian to help with experience, but the remaining players are still rather inexperienced at top level.
7.31pmPREDICTION! We've got just under 15 minutes until kickoff and it's time for me to make a prediction... The away goal will be a slight help to the Hammers, but you do not expect that they will want to be sitting around waiting for a 0-0 draw at home. Looking through their lineup you cannot really see them slipping up here. Bilic has made a number of changes although this side still has so much to offer. I fancy the hosts walking this with a 2-0 victory to take things 3-1 on aggregate.
7.35pmSo how will United go about their work this evening? You'd think that Bilic will be wanting his side to put this game to bed as early as they possibly can and do not be surprised to see the Hammers take the game to their opponents from minute one. The worst thing they'll want is to be chasing this game in the latter stages in front of an expectant crowd.
7.37pmBilic will be hoping that his team are more clinical than they were last week. Antonio should have put this game out of sight and they were made to pay by Alibec, who again starts here.
7.38pmFor all of you Hammers fans, the club have just announced this exciting piece of news prior to kickoff:
7.38pmThe West Ham fans in the ground clearly recognise the importance of bringing European football to this group. They're in full song already at the London Stadium, which is awash with colour five minutes prior to the start of the match.
7.42pmBilic has just made his way out to his seat and we're looking at just about a sell-out here in east London. The players are now in the tunnel, what a fixture we have ahead of us!
7.43pmAnd we're out as bubbles fill the air and the West Ham United faithful open up into full song, the atmosphere here is electric...
1 minKICKOFF! The visitors, dressed in white, get us underway. They soon lose possession and Obiang can break forward with speed, before he is eventually cut out by Fabricio.
3 minThe away side have shared most of the ball in the first few minutes, but the Hammers have pressed with intent to put them under some early pressure. Tore gives away a needless free kick, giving Astra the chance to lump something forward. The ball comes in via Morais, leaving Randolph to gather on his line with ease.
4 minUnited aim to open up the flanks for the first time as the ball is shifted deep into the path of Tore, but the delivery has just too much on it and runs out for a throw. The winger could have been in there with a little more control on the ball.
7 minTore shows some neat skill down the right and is able to win a cheap free kick off Seto. The wide-man then gives possession away carelessly with the pass and Astra can break. The move comes to Alibec, who tries something spectacular from distance, which sees the ball go flying high and wide of Randolph's goal.
8 minNot too much to report in the first 10 minutes here. West Ham have assumed early control in the middle, but neither side has been able to put much together going forward in the final third.
9 minCHANCE! Wonderful stuff from Burke. The full-back spots the run of Calleri in behind and is able to produce the cutest of through-balls to find the striker. The frontman only has the keeper to beat, before getting his feet mixed up and firing a shot straight at a grateful Lung in the away goal. It should be 1-0 to the hosts...
10 minObiang seeks to move the ball quickly across the middle in order to find a ball out for the run of Tore. It looks perfect on paper although his execution is poor as the ball flies out for a throw. The home side are starting to show a little more adventure now as the game progresses through the early stages.
14 minSAVE! The pace has slowed a notch now as West Ham look for the final ball. Antonio comes inside to pick out Obiang, who unleashes a thunderbolt from distance that requires Lung to tip the ball wide of his post down low.
16 minCHANCE! From the corner, Tore puts in a perfect ball into the middle which results in a huge scramble. It looks like the Hammers might just get a deciding foot to the ball, but Astra clear at the vital moment and are then awarded a foul for some supposed pushing inside the area.
17 minThe home side are seemingly slipping into something beyond second gear, this time as Antonio comes in on his right and flashes a wild shot across goal and wide thanks to a kind deflection. The corner comes in, where Alves is able to head clear.
18 minCLOSE! Tore shows some more impressive skill before being pulled down on the right wing. The playmaker then bends a wonderful cross into the penalty area, with the delivery running just beyond the reach of an on-rushing Reid.
20 minThe counter almost ends up being fruitful for the hosts who break away through Antonio. It looks like his well-crafted pass might just match the run of Obiang, although Alves gets back at the vital moment to steal in and clear the danger.
24 minAstra are enjoying a short spell of possession which is being matched by some efficient shuffling from the Irons. It's a little congested in the middle at times and the wings look like a very appealing option at the moment.
26 minBurke gives the ball away on the left channel and the full-back thinks that he deserves a free kick for his troubles. Luckily for the hosts, Antonio races back in order to take the ball off an advancing Lovin.
28 minYELLOW CARD! Pure stupidity... Alibec drifts out to the right win to receive a long ball forward. There's no need to make a challenge, but Reid steams in before receiving a yellow card for a late tackle on the striker.
29 minCLOSE! Almost a shocker from Lung in the Astra goal. The keeper steps forward to send a straightforward kick out to his players until he scuffs his effort into the path of Calleri. The striker can't get things under control and the stopper is able to reclaim the ball.
31 minWest Ham are suffering from a lack of forward runners from the midfield. The wingers are doing all they can to create space but they're going to need to take a gamble somewhere in the middle if they want to unlock the Astra defence.
35 minThe visitors are standing firm at the moment and aren't afraid to venture forward when possible either. You feel that West Ham need to up the pace a touch, everything is a bit too slow at the moment and Astra have had a fairly good read on the game so far.
38 minTore has switched over to the left of the pitch and he provides a mazing run before picking out the movement of Burke. The youngster finds himself in a good position to cross, but his final touch lets him down and his delivery balloons out for a goal kick.
41 minReid races forward and comes up short when he is tackled on the half-way line. Astra burst forward with Alibec, who is eventually intercepted by a standout tackle from a retreating Nordtveit. The visitors will be more than happy with their work thus far. They only need a goal at the moment...
43 minBilic will be slightly frustrated by what he has seen in the last 10 minutes. The Hammers have plenty of room on the pitch but aren't using it properly. They're pace has been down and they've lacked invention...
45 minGOAL! WEST HAM UNITED 0-1 ASTRA GIURGIU (Filipe Teixeira)
45+1 minWhere did that come from? Burke gives the ball away on the left in an attempt to break forward and the ball is quickly threaded over to Filipe Teixeira who finds himself free in space on the left. The frontman moves forward inside the area before lashing a tidy finish into the bottom corner beyond Randolph. Now that is how you launch a counter!
45+2 mnHALF TIME: WEST HAM UNITED 0-1 ASTRA GIURGIU
8.33pmSo the referee calls a halt to an interesting first half of football at the London Stadium. West Ham started well and should have found themselves ahead, but Bilic's men stepped off the gas and have faded disastrously. Astra have been in the game all along and finally capitalised on some sloppy passing to launch a wonderful counter attack that leaves the visitors on course to knock the Hammers out!
8.41pmWhat can West Ham do to change this? A little help going forward from the midfield might help... Bilic's men aren't doing themselves any favours with the speed of their passing either. Things are just too slow for this European occasion. The Hammers need two goals now to do this within normal time, a leveller would take things to extra time.
8.48pmHere we go then, the second half is just around the corner... How long will Bilic wait before he makes changes. Sticking someone like Fletcher up front might help with his height and add a bit of urgency.
8.49pmSUBSTITUTION: We're seeing that Enner Valencia is going to be introduced, he'll be coming on in place of Nordtveit. Valencia hasn't scored since January, mind...
45 minKICKOFF! The Hammers get us moving again and they seemed to have switched to a straight out 4-4-2 in the second half. Valencia will partner Calleri in attack.
47 minNot the best of starts for the Hammers, who appear a little bit shaky in the early moments of the second offering. Byram should clear easily but makes a mess of his attempt and Reid has to steal in at the crucial moment to deny Niculae.
49 minCalleri tries to spring a counter for the Irons as he tears away down the middle of pitch. The forward tries to get the better of Sapunaru, but the full-back stands strong as the visitors' last man.
51 minBetter! More pressing and quicker passing from the hosts. Tore moves out wide before seeing his cross cleared for a corner. The ball into the box finds the leap of Ogbonna, who sees his effort comfortably saved by Lung.
53 minCLOSE! Lovely from Tore who takes the ball out of the air with one touch in order to flick the ball around the corner for the run of Calleri. The frontman just doesn't quite have the legs for it and Fabricio clears.
54 minCLOSE! He has to do better surely? Tore curls a peach into the area for Calleri, who heads down onto his shoulder to allow Lung to make a good save down low. Poor technique from the striker. If he connects cleanly with his head that's a certain goal - he's missed two standout chances now.
58 minSUBSTITUTION: Astra make a change as Niculae is replaced by Cristian Oros.
61 minSUBSTITUTION: Bilic makes another change now as Calleri is replaced by young forward Ashley Fletcher.
62 minCLOSE! What a chance... Tore has the chance to whip a corner into the middle and he responds with an absolute peach. Reid is the first to it but can only glance his header agonisingly wide of the far post.
63 minThis change in pace has worked wonders for West Ham, although they have to take their chances when they come. The hosts have 30 minutes to change the course of their European prospects this season.
65 minStill West Ham keep the ball inside the Astra half, but the visitors are not moving an inch. You doubt they'll be aiming to score another tonight and the remainder of this game is all about the Hammers trying to break them down.
67 minValencia has been disappointing since coming on, he was introduced in order to make some runs in behind but we've seen nothing of the sort. The tempo has gone up only for the creativity to remain at its same low levels as the first half. The home support are getting a tad jittery with just over 20 minutes to go.
69 minThe crowd go up with shouts for a penalty as Reid sends the ball into the box. The referee responds by giving a free kick in favour of the visitors, though, having called up Antonio for pushing his marker to the floor.
70 minPENALTY SHOUT! Some standout work from Fletcher sees him beat three players down the right. The youngster drives into the box before going down under the challenge of a retreating Teixeira, only for the referee to wave play on. The hosts need more of that kind of running as we go into the final embers of this game.
72 minBurke gets some room down the left as he links up with Fletcher. The ball towards the back-post finds Valencia leaping highest, but he cannot get his head to the ball as Astra come away with a goal kick.
74 minCLOSE! A big scramble inside the area sees the ball fall to Obiang on the edge of the area. The midfielder drills a shot into the melee, before the ball falls kindly for Fletcher in behind the defence. He turns and shoots in one motion, only to be denied by the legs of an outstretched Lung. What a save from the keeper...
76 minCHANCE! Fletcher has been a breath of fresh air since coming on, very direct. The youngster wins a cheap free kick right on the edge of the area with some wonderful footwork before being upended by Oros. Valencia stands over the kick and bends an absolute peach over the wall, where he is stopped by the firm hands of Lung who sees the ball very late.
78 minCLOSE! Interesting... A superb ball over the top finds Antonio through on goal, where the winger slots the ball effortlessly beyond the Astra keeper. The goal does not count though, as the referee spots the slightest of pushes on full-back Alves.
79 minThings are getting slightly more desperate now as the Hammers pour forward more out of hope than anything. Can they muster something in the final 10 minutes? As it stands, they're going out of this tournament before the group stages.
84 minThe visitors look set fair at the back now and they will be hoping to see out these final storms from West Ham. Other than Fletcher, the hosts have shown very little going forward to merit getting anything out of this game.
86 minCan West Ham find one moment of quality to take this into extra time? Not on the current evidence. The hosts are moving things well up until the vital moment, where they appear to be rushing things.
87 minCLOSE! A scramble at the back sees the ball run kindly for Valencia, it looks like he's about to stick the ball beyond Lung, only for Oros to steal in with a potentially match-winning challenge.
89 minYELLOW CARD! All hands to the pump now for Astra who break forward with Stan. The substitute does enough to waste some before West Ham win the ball back. It goes long into Collins, who fouls his opponent to give away yet more time. Silly challenge really, and he goes into the book too...
90 minYELLOW CARD! Astra will love this! Antonio only really has eyes for the ball as he goes for a turn and volley, where Seto nips in to earn a free kick and hand his opponent a yellow card.
90+1 minWe're going to have five minutes of additional time here...
90+3 minSome hard work from Antonio comes to nothing on the right as he gives away a throw to the visitors. Can they see this through?
90+4 minOnly scraps for the Hammers to feed off in injury time. A long ball is aimed for Collins, who misses his touch and the ball runs comfortably through for Lung.
90+5 minFULL TIME: WEST HAM UNITED 0-1 ASTRA GIURGIU
90+5 MINASTRA GIURGIU ADVANCE TO THE GROUP STAGES OF THE EUROPA LEAGUE
9.43pmWell there we have it, who could have predicted that? West Ham bow out without even making the group stages of the Europa League. What a shame for all these fans inside the London Stadium. This sort of ground demands European football. That said, the Hammers just did not do enough to win this match and only really started playing after going behind. Fletcher was a bright spark in a very dull and potentially worrying showing for Bilic's side. As for Astra, they did exactly what was required - they grabbed the all-important goal and defended right until the death... That's going to be all from me tonight, thanks for joining us!