West Ham booked their place in the last eight of the FA Cup thanks to Frederic Kanoute's 76th minute strike.
The Frenchman latched on to Frank Lampard's precise through ball to slot the ball past Thomas Sorensen and send the visiting Hammers fans into raptures.
Only moments earlier, Lampard should have found the net but his weak shot failed to trouble Sorensen.
Sunderland, who were without Don Hutchison for the clash, fought tirelessly all afternoon to break down a resolute Hammers defence and 37-year-old veteran Stuart Pearce was particularly impressive for the visitors.
Sunderland's only real chance of the game fell to John Oster but Shaka Hislop was equal to the Welsh international's long range drive.
On the back of wins against Manchester United at Old Trafford and today's victory at the Stadium of Light, West Ham must now be considered as serious cup candidates and very few would bet against Harry Redknapp's side lining up at the Millennium Stadium in May.
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