
Louis Saha scored twice, while Wayne Rooney and Cristiano Ronaldo, with a superb strike, got the others as United won 4-0 at Sunderland to go a point clear of Arsenal, who could only draw at Portsmouth in the late game.
Chelsea are now seven points behind United after they were held to a 4-4 draw by Aston Villa, while Liverpool are just two points further back, with a game in hand, after they snatched a 2-1 win at bottom side Derby County thanks to a late Steven Gerrard goal.
At the Stadium of Light, Sunderland held out for 20 minutes for manager Roy Keane against his former side, but once Rooney had opened the scoring on 20 minutes, there was only going to be one winner.
Saha made it 2-0 within 10 minutes and a stunning free-kick from Ronaldo put United 3-0 up on the stroke of half-time. Sir Alex Ferguson's side eased off in the second half, but Saha made it 4-0 from the penalty spot when Nani was fouled.
"It was an excellent performance, I thought the passing and movement was excellent," Ferguson said.
"The first goal put us in the driving seat because we knew Sunderland were going through a bit of a sticky patch.
"It was a marvellous move for the first goal and after that, we did play well."
William Gallas missed the best chance of the game with three minutes to go at Fratton Park as Arsenal were frustrated by a strong defensive performance by Portsmouth.
David James made a good save to prevent Tomas Rosicky from scoring in the first half, but otherwise the Portsmouth goalkeeper was not overly tested, though Rosicky shot just wide in injury time.
At Stamford Bridge, an upset looked more than likely when Shaun Maloney scored twice to put Villa 2-0 up after 43 minutes.
But Zat Knight was sent off for a professional foul on Michael Ballack on the stroke of half-time and Andriy Shevchenko scored from the penalty spot.
Shevchenko smashed in the equaliser from 20 yards soon after the restart and Alex put them ahead just after the hour mark - only for Martin Laursen to make it 3-3 with 20 minutes to go.
Germany captain Ballack - who came on early as a substitute for injured Frank Lampard - then scored from a free-kick as Chelsea seemed to have clinched it, only for Barry to deny them from the spot.
Chelsea manager Avram Grant defended Ricardo Carvalho, who was sent off with 10 minutes to for a nasty tackle, but Aston Villa manager Martin O'Neill thought his side were well worthy of a point.
"We deserved nothing less than a draw. We were terrific," he said.
"In the first half we were 2-0 in front just before half time, were playing brilliantly and deserved to be in front.
"We never gave up and came back from the dead twice."
In other action, Liverpool moved above Manchester City into fourth and closed to within two points of Chelsea after a 2-1 win at Derby County, thanks to Steven Gerrard's late winner.
"We were much better in the first half, but we could not kill the game off," Liverpool manager Rafael Benitez said.
"That made it difficult for us. In the second half they were more aggressive and they put us under a lot of pressure.
"We gave the ball away too much but in the end Gerrard scored, a player like that will always come to the fore in the end."
Everton are just a point behind City in sixth after a 2-0 win over Bolton Wanderers, with goals from Phil Neville and Tim Cahill.
Wigan Athletic moved out of the bottom three - above Sunderland and Fulham when Ryan Taylor's second-half strike lifted them 1-0 over Newcastle United.
Tottenham Hotspur hammered Fulham 5-1, with Roy Keane and Tom Huddlestone both scoring twice. Birmingham City beat Middlesbough 3-0 and West Ham United and Reading drew 1-1 at Upton Park.
By Ben James, dpa