The pair are expected to face off for a second time before the year is out, as Klitschko seeks revenge for his 11th-round defeat to undefeated Joshua in front of 90,000 spectators at Wembley Stadium in April.
Cardiff's Principality Stadium had been touted as a possible venue for the event, with October 28 the date provisionally pencilled in, but despite Hearn being keen to keep the fight in Britain the lure of Vegas could be too much to turn down.
"I have been in talks with Bernd Boente and the team," he told Sky Sports News. "We're getting close now to identifying the real options in terms of venues and locations. Vegas has taken a little bit of a frontrunner in those. I know the British fans would love to do a trip out there for Joshua-Klitschko.
"Nigeria is still in the mix, Dubai as well, and of course Cardiff. But like I said, Vegas has probably got its nose in front at the moment. I think in the next week, we're looking to present all those opportunities to Wladimir Klitschko and his team. Speaking to Bernd Boente this morning, I feel like it's going to take that special event to make this fight.
"I would like to keep it in Britain," said Hearn. "The fans have been incredible to Anthony Joshua, but if it means travelling to make sure this fight happens for world boxing, and it means taking a few plane loads to Las Vegas for a night and an experience they won't forget.
"Anthony Joshua is the world heavyweight champion, he's not the British heavyweight champion. He wants to break boundaries and so do we. To see Anthony Joshua's name up in lights on the Las Vegas strip is certainly something that appeals to us all. I would say the next couple of weeks, we'll be looking to make a decision in terms of the venue and location."
Kubrat Pulev remains the mandatory challenger for Joshua's IBF belt should Klitschko opt against invoking his rematch clause.