Ferdinand, 23, joins for an undisclosed fee, believed to be around £8million.

The former England Under-21 centre-back said:"It was hard leaving West Ham because I have been there for 16 years but after meeting Roy Keane I knew it was time for a change.

Roy Keane on Ferdinand's signing >>
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:"This is a great challenge for me and I feel it is an exciting time at Sunderland. I think the move will do me good"

The player will have to wait for his debut, as he recovers from a hamstring strain. His first chance could come at Wigan on September 13.

Manager Roy Keane said: "We needed to strengthen our defence and Anton is a great signing. He's still young but he has over 160 games under his belt so he has experience, he's learning his trade.

"He'll bring quality and competition for places which is what we want, hopefully we can take him to another level here at Sunderland. He has come through the ranks at West Ham and maybe just needs a change."

Keane wants one more player - probably a left-back - before the transfer window closes next week.

"I have one more player in mind and then that is the end of it for a few months at least," he said.