The Tigers suffered a 3-2 defeat in the FA Cup final to Arsenal at the weekend, but have qualified for next season's Europa League.
They will face a number of qualifiers to reach the group stages and Bruce admits that his current squad is not ready for the rigours of European football.
"We have to look forward to European football and we will have to try to enjoy it, but whether we have got the resources and the manpower, I am not so sure," Sky Sports News quotes him as saying.
"We certainly need another five or six players. We've got two, three or four who are out of contract, so we'll now decide what we're going to do and plan a way to come back again.
"We have to improve, to get better, because you cannot stand still. I think we've got four European games by the end of August. And a club like ours, I don't think we're ready for that. But we'll have to give it a shot when it comes around."
Hull finished the season 16th in the Premier League table.