Frank Lampard hit four goals for Chelsea in a 7-1 demolition of Aston Villa to put the Londoners briefly on top with 71 points before United responded with a 4-0 win in an evening game at Bolton Wanderers - Dimitar Berbatov scoring twice for the champions.
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United, chasing a record 19th top-flight title, have 72 points while Arsenal are third on 68 after Birmingham City netted in stoppage time to rescue a 1-1 home draw against the Gunners.
Tottenham Hotspur strengthened their grip on fourth spot with a 2-0 home win against relegation-bound Portsmouth while West Ham United lost 1-0 at home to Stoke City, their sixth league defeat in succession.
West Ham are out of the bottom three only on goal difference after Hull City matched them on 27 points with a 2-0 victory over Fulham.
Wolverhampton Wanderers maintained their improved form with a 0-0 draw against Everton.
United and Chelsea, who meet next week at Old Trafford, both rested players on Saturday but even with the likes of Wayne Rooney, Didier Drogba and Rio Ferdinand having a day off, they produced performances worthy of champions.
As the season enters the stage where dropped points at either end of the table are magnified, the leading two were impeccable, although Chelsea did suffer a first-half setback against Villa before putting their opponents to the sword.
Lampard reached 151 goals for Chelsea to become the club's third-highest scorer of all time, two of his four strikes coming from the penalty spot.
"When you take the work ethic the guy's got, it's no fluke, he works so hard day in day out. It's first class," Chelsea assistant manager Ray Wilkins told reporters.
"When you've consistently scored goals and played the way he has for so many seasons you have to say he is world class."
The England midfielder gave his side an early lead from Florent Malouda's low cross-cum-shot but Villa, Chelsea's FA Cup semi-final opponents next month, deservedly equalised through John Carew.
Lampard restored Chelsea's lead shortly before halftime from the penalty spot after Yuri Zhirkov was brought down by James Collins and the second half was a romp for Carlo Ancelotti's side as they followed up their 5-0 defeat of Portsmouth in midweek.
Malouda made it 3-1 just before the hour before Lampard completed his hat-trick, beating keeper Brad Friedel again with a spot kick after Zhirkov was once more fouled in the area.
Lampard set up Malouda for Chelsea's fifth, Salomon Kalou made it six and Lampard struck again late on to chalk up his 100th league goal for the club.
If Ancelotti had hoped for a favour from Bolton he was to be disappointed as the hosts gifted United the lead before falling apart in the second half.
