United's 3-0 win over a Liverpool side reduced to 10 men just before halftime with the expulsion of Javier Mascherano and Chelsea's come-from-behind 2-1 win over Arsenal saw the clubs who have won the last three titles between them move ahead with seven matches to play.
United, who still have to play Arsenal at home and visit Chelsea, have 73 points, five more than Chelsea who moved above Arsenal into second place on 68 points.
Arsenal, who were top of the table at the start of March, slipped back to third on 67 points after a fifth league match without a win.
Arsenal, the last team to beat Chelsea in a league match at Stamford Bridge 78 games ago in February 2004, took the lead after 59 minutes with Bacary Sagna scoring his first goal for the club.owever, despite playing their part in a superb match, poor defending from Arsenal allowed Didier Drogba to score twice in the closing stages to give Chelsea a priceless win.
Liverpool, who had to win at Old Trafford to retain any chance of a first championship success since 1990, remain in fourth place on 59 points and are out of contention.
Rafa Benitez's side went into the match enjoying a seven-match winning streak in all competitions but were comprehensively beaten by United who won for the fifth straight league game.
A rare goal from Wes Brown -- only his second for United in 10 years -- set United on their way with late goals from Cristiano Ronaldo and Nani wrapping up the points.
Mascherano's dismissal provoked an angry response from coach Rafa Benitez and his men while Mascherano could find himself in more trouble after taking time to leave the field.
Liverpool's defeat at United increases the pressure on them to maintain their grip on fourth place and a coveted Champions League qualifying berth.
Although Everton were held to a 1-1 draw at home by West Ham United on Saturday, they have moved to within two points of Liverpool, with the two teams due to meet at Anfield next weekend.
Elswehere on Saturday, Derby moved a step closer to their inevitable relegation with a 1-0 defeat at Middlesbrough, while Fulham also moved closer to the drop after going down 2-0 at Newcastle United, who won for the first time in 10 matches since Kevin Keegan returned to the club as manager in January.