United had thrown everything but the metaphorical kitchen sink at the Black Cats, but Sunderland held firm until seconds into four minutes of injury time.
Then, United's star man, Michael Carrick, produced a decisive 25-yard shot. The ball took a deflection off Sunderland defender Anton Ferdinand and rattled the inside of the left post.
As the ball rebounded across goal, United's Serbian defender Vidic pounced to score with a left-foot shot from five yards at the far post.
It was a heart-breaking finale for Sunderland and their caretaker manager Ricky Sbragia, a former reserve-team coach at Old Trafford.
Sunderland's recently departed manager Roy Keane would have been proud of the way his former players battled to keep United at bay.
But the former United hero would also have admired the never-say-die spirit of his old side which he epitomised so well during his golden years as a player at Old Trafford.
United passed Sunderland to death, but the Wearsiders' policy of holding onto a point at all costs was reflected in the fact that first Djibril Cisse and then Kenwyne Jones were lone marauders up front.
The statistics do not lie. Sunderland created only one real chance in the game - El Hadji Diouf's cross-cum-shot from the left by-line in the 70th minute which United goalkeeper Edwin van der Sar saved with his legs.
Sunderland's only corner came in the 89th minute and forward Diouf spent more time in his own penalty area than in United's.
Sunderland also had reserve goalkeeper Marton Fulop to thank for keeping the Red Devils at bay.
In the 12th minute, Cristiano Ronaldo flicked a pass from Darren Fletcher into the path of Dimitar Berbatov just inside the Sunderland box and Fulop did well to save the Bulgarian's shot with his legs.
Fulop also used his legs to keep out another United effort, this time from Ji-Sung Park in the 28th minute.
It took two attempts to save Carrick's 25-yard drive in the 54th minute and Ronaldo went off in bizarre circumstances in the 66th minute.
Turning awkwardly, the Portuguese winger deliberately kicked the ball out of play and then left the pitch, walking straight down the tunnel rubbing his left side as he departed.
United continued to pile on the pressure as Carlos Tevez, Ryan Giggs and Anderson entered the fray, but Sunderland held on almost until the bitter end.