Manchester City, whose manager Roberto Mancini conceded on Thursday that their hopes of retaining the title were over, beat visiting strugglers Newcastle United 4-0 with goals from Carlos Tevez, David Silva, Vincent Kompany and Yaya Toure.
With United's match having kicked off earlier on Saturday, City took the field at the Etihad Stadium 18 points behind their rivals who set a top-flight record of 25 wins from their opening 30 matches. United have 77 points with City second on 62.
Arsenal's victory, with goals from Gervinho, Santi Cazorla, Olivier Giroud and a late Mike Arteta penalty, meant Reading, who had new manager Nigel Adkins in charge for the first time, dropped to the bottom below Queens Park Rangers.
The decisive goal in Manchester United's win at Sunderland came after 27 minutes, when Robin van Persie ended a jinking run on the left with a shot that took a deflection off Bramble's thigh, leaving Black Cats keeper Simon Mignolet stranded.
"Of course, no question about it. It's been a while so it's nice to score again and it was an important goal," the striker told Sky Sports.
It was United's seventh successive league victory and their sixth league game without conceding a goal. Their 25th win from 30 league matches was the best record in the top flight at this stage of the season since league football began in 1888.
"It was a battle in the second half and you have to give Sunderland credit as they had a real go at us," he told the BBC.
"We picked up two or three injuries and our goalkeeper was hurt so it was a real battling performance. We've got to win four games out of the last eight and it's important we focus on the Manchester City game, which is next at home."
