Vassell returned early from Villa's pre-season tour of Sweden to talk things through with City officials. The arrival of Kevin Phillips at Villa from Southampton has increased competition for places.
Vassell, who has a year to run on his contract, was informed by Villa manager David O'Leary he could go. O'Leary told the club's website: "Darius was asked to go back to England and there was no reason to stop him. It all happened very quickly yesterday and we were able to get him on a flight.
"He's gone back to have a medical and sign for Manchester City. I can't say at the moment what the exact fee is, but I think it's a fee that suits Aston Villa."
Vassell has had a miserable time since his decisive penalty miss in England's European Championship shoot-out with Portugal last summer. He scored just one Premiership goal in 10 games before breaking his ankle against Fulham.
That sidelined him for four months and when he returned he was unable to inspire Villa to a European place - they finished 10th.
O'Leary insisted financial constraints had not forced the sale. "It's not fair to say that I had to sell Darius to bring in money. That would be totally unfair on the club. This is a good deal. We've been offered good money by Manchester City, so it suits everybody all round as it stands. But who knows - the player could go up there and fail to agree terms, so it's not done yet."
The Everton chief executive, Keith Wyness, is hopeful of tying Tim Cahill down to a long-term contract despite reports claiming the winger has rejected their latest offer. The Toffees signed the Australian from Millwall for £1.5m last summer and he proved influential as David Moyes' side qualified for the Champions' League.
After such a successful first season in the Barclays Premiership, Everton are keen to extend Cahill's contract beyond the three years it has left to run. The 25-year-old, however, has apparently rejected their latest advance. Wyness said: "We have been in discussions with Tim Cahill and he still has three years left to run on his current contract. Talks will continue, but we want him to stay with us for a long time."Reuse content