As excusively revealed by Sportsmail earlier this year, the Atletico Madrid goalkeeper - who helped Spain to Under 21 Euro glory on Saturday - has been pinpointed as the successor to Edwin van der Sar, who retired at the end of the season.
The deal for De Gea is expected to be finalised in the coming days and will take United manager Sir Alex Ferguson's summer spending past the ?50m mark.
Ferguson has already recruited England pair Ashley Young and Phil Jones - from Aston Villa and Blackburn respectively - for a combined fee of ?32.5m.
Although Ferguson considered deals for Manuel Neuer and Maarten Stekelenburg, who are now heading for Bayern Munich and Roma respectively, De Gea quickly emerged as his No 1 target.
This is despite the 20-year-old's inexperience, having only been first-choice at Atletico for the past two seasons.
But Liverpool keeper Pepe Reina - an international team-mate of De Gea - has backed the youngster to shine in the Barclays Premier League next season.
All over: Edwin van der Sar called time on his playing career at the end of the season
He told La Gaceta: 'I very much welcome this news because David is a great keeper. When it becomes official he is going to start working to prove in the Premier League what a good goalkeeper he is.'
Reina, who is currently on holiday in Ibiza, has also rejected claims that he will now head back to Spain to replace De Gea at Atletico.
He added: 'I know Atletico are looking for a goalkeeper, but I won't be changing colours. I have a five-year contract and I'm happy at Liverpool.'
Source: Daily Mail