The Italian club are keen to re-sign Veron, who moved to United for �28.1m last summer.

"It is very possible a swap deal will be done with Manchester," Lazio spokesman Guido Paglia told The Guardian newspaper.

"Lazio president Sergio Cragnotti likes Veron very much and he will always be popular with our supporters.

"We would like him back but we must wait until August before initiating moves.

"If Manchester contact us before then with a proposition to sell Crespo, we will start discussions but we are waiting for news from Veron's agent Gustavo Mascardi."

United need to strengthen their attacking options after selling Dwight Yorke to Blackburn for �2m.

Crespo signed for Lazio for �35.7m in 2000 - a world- record fee at the time.

He was a member of the Argentine World Cup squad, making three substitute appearances before his team were eliminated from the tournament at the end of the group stage.

Crespo was also a team-mate of Veron at both Lazio and Parma before the midfielder's move to England.

Meanwhile, United have denied that Verron will miss the start of the season with an Achilles tendon injury.

It had been reported that the Argentine midfielder needed an operation - but United insist this is not the case.

"Juan Sebastian Veron is in the squad to play Bournemouth on Saturday and it is highly unlikely that we would risk him if he were facing an operation," said United's director of communications Paddy Harverson.

"There has been no talk at Manchester United of Seba facing an operation."