The longest-running saga of the summer has reached a confusing climax after an earlier statement that he was staying at Villa Park.
Sportsmail understands that the mix-up was due to a deadline being missed by 20 minutes, and the transfer will finally be concluded on Thursday.
Villa will receive a £17.5million fee plus right back Steve Finnan in exchange for a midfielder who will fulfil his wish to play in the Champions League this season after all.
To find the money, Liverpool needed to provide the bank with a guarantee that funds to cover the move will be raised during the remainder of the close season.
The transfer has dragged on since May when Liverpool boss Rafa Benitez made it clear that Barry was his top priority.
Villa manager Martin O'Neill was angry with him for making details of his interest public, and a war of words raged between them for much of the early summer.
Liverpool made four separate bids to sign Barry but none of them matched O'Neill's valuation of the player.
Barry's outburst against O'Neill in a Sunday newspaper then appeared to signal the end of any chance of him remaining at Villa.
He accused the manager of finding time to be a pundit at Euro 2008 but not to speak to him about his future and was disciplined and told to stay away from the club's training ground.
Then Barry was booed by Villa fans at a pre-season friendly at Walsall last week, but that mood had mellowed when he appeared as a substitute in Saturday's InterToto Cup tie with Odense.
Matters finally reached a head on Monday when O'Neill tried to force the Merseysiders into a corner by setting a deadline. That was passed at 5pm on Wednesday when Villa had still not received confirmation from Liverpool chief executive Rick Parry that funds were in place.
Villa then put out a statement on their website confirming that Barry would be staying. It read: 'This evening, Aston Villa can announce that Gareth Barry will be staying with the club following the interest from Liverpool over recent months.
'During discussions in the past few days, a final deadline to conclude this episode was set that all parties were aware of and agreed to. This deadline has now passed and so Gareth will remain with Villa.'
However, it soon transpired that the two clubs were still talking over the move. Barry had been due to play in a behind-closed-doors friendly against Notts County on Thursday - but his name was subsequently withdrawn.
And it also appears that the England midfielder has already committed himself to renting a house in Cheshire.
The transfer has dragged on but now Benitez has to act quickly by offloading players to keep Liverpool's part of the bargain with financiers.
Those destined for the exit door include Andriy Voronin, Alvaro Arbeloa, Xabi Alonso and Jermaine Pennant.
Following David Bentley's defection to Spurs, Pennant will probably be the first to leave as Blackburn manager Paul Ince spends some of the transfer money he has received.
Robbie Keane kicked off his Liverpool career against Villarreal in Spain, two days after completing his £19m move from Tottenham. The Republic of Ireland captain started up front alongside 19-year-old David Ngog, who cost £1.5m from Paris Saint-Germain.