The former French international passed his medical and was unveiled at a media conference at Old Trafford on Thursday.

Blanc has been lined up as a replacement for Jaap Stam, who joined Lazio for �16.5m on Monday.

United boss Sir Alex Ferguson opted not to attend a G14 managerial conference in Geneva in order to sign the veteran French defender.

And a delighted Ferguson said: "This is maybe the fourth time we have tried to get him.

"I have tried in the past to do it, even last season - but it has always been the wrong time.

"We've followed him around the world but now we are delighted he has joined us.

"Laurent's experience will be vital to the younger players like Mikael Silvestre, Wes Brown, Gary and Phil Neville."

Blanc played down reports that he had not wanted to sign for the Old Trafford club, saying that something had always got in the way before.

The Frenchman added: "I am honoured to play for such a big club like Manchester United.

"I never refused them. There was always something that prevented the transfer. That's all."

United were eager to complete the move before Friday's Champions League transfer deadline so that the 35-year-old would be eligible for their European campaign.

Blanc's addition to the United squad will come as a welcome boost for Ferguson.

PSV Eindhoven, Parma and Valencia have let the United boss know that they have no intention of selling Kevin Hofland, Fabio Cannavaro and Roberto Ayala respectively.