The 30-year-old has signed a three-year contract and his registration was pushed through in time to make him eligible for Saturday's trip to Sunderland.

Manager Sir Alex Ferguson has been pursuing an extra goalkeeping option for some time with Fabien Barthez still recovering from a hip injury.

"The important thing with Ricardo is that he is available for European football," said the United boss.

"He is second choice in the Spanish national squad and a lot of people believe if he was with a bigger team he would be in the side.

"With that level of ability he was an easy choice.

"The concern over Fabien meant we had to move for a third goalkeeper and it is always good to have that competition for places.

"Challenge is always there no matter what position it is. A new player can command his place by his performance on the field."

Ricardo made his first-team debut for Atletico Madrid in 1995.

He returned to the reserves in the 1997-98 season before moving to Valladolid at the end of that campaign.

Last season was the first time he made regular appearances in the First Division, playing 38 league matches and winning a call up into the Spanish national squad.

He was included as third-choice keeper in the World Cup squad, but following the injury to Santiago Canizares he ended up deputising for Real Madrid's Casillas.

"As a child I followed the English league and I believe at the moment it is the best league in the world," a delighted Ricardo told United's official website.

"As a footballer you always try and get to the top and be the best and I think I have arrived at one of the best clubs in the world."

Ferguson had feared the deal would not be concluded in time for his new arrival to face Sunderland.

But Ricardo is now likely to make his debut at the Stadium of Light at the expense of Roy Carroll.

While Carroll has performed admirably in the absence of first choice Barthez, the Northern Ireland international's inexperience was exposed on United's last league outing at Chelsea.