Alex Black wants United to clarify his client's position as soon as possible.
"I think if you're definitely not wanted, you need to be told that," Black said on BBC Radio Five Live.
Black revealed Smith has been concerned about his future ever since United chose not to exercise a clause in his contract, which would have seen it extended by another year to 2010.
"Obviously, you're going to have some question marks in your head as to where that leaves you," said Black, adding that Smith is not looking for a guarantee of first-team football.
"Nobody would expect that at a club like Manchester United," he said.
Unless United make the first move, Smith is set to remain in limbo until the start of pre-season training.
"Alan's gone away on holiday for a few weeks and these are the sort of conversations that probably need to take place face to face," Black said.
"I'm sure him and Sir Alex will have a chat at the start of pre-season.
"The only conversation so far that's taken place has been between myself and David Gill, the chief executive, and that was brought up regarding the re-negotiation clause."
Asked whether he and Smith would actively look for another club, Black said: "It's not really for us to look at other clubs.
"Our opinion is he hasn't been offered a new contract but he's still got two years left at arguably the biggest football club in the world.
"He has the confidence in himself to stay and fight."