Manchester United moved to within touching distance of the Premiership title after Cristiano Ronaldo's penalty gave them victory at Manchester City.
Ronaldo scored in the 34th minute after he was fouled by Michael Ball - who had earlier stamped viciously on the star.
City wasted their best chance when goalkeeper Edwin van der Sar saved Darius Vassell's penalty 11 minutes from time after Wes Brown fouled Ball.
Chelsea must now win at Arsenal on Sunday to keep alive the title race.
606: DEBATE
The game opened in shameful fashion, with City defender Ball guilty of a cowardly stamp on Ronaldo as the United winger lay on the ground.
Referee Rob Styles was unsighted but Ball is unlikely to have heard the last of the disgraceful foul and United manager Sir Alex Ferguson was understandably raging on the touchline after watching a replay of the incident.
City, without a league goal at home since New Year's Day, had a half-chance to end that barren sequence after 16 minutes but Emile Mpenza shot straight at Van der Sar.
United were displaying all the real quality, despite City's rather obvious attempts to entice them into a physical battle as opposed to a football match.
Rio Ferdinand should have given the visitors the lead in the 23rd minute but he headed against the bar from close range after Ronaldo flicked on Ryan Giggs' corner.
Ronaldo exacted revenge on Ball after 34 minutes when he tempted the defender into a foul inside the area - the Portuguese star recovering to send Andreas Iskasson the wrong way from the spot.
The second half was a desperately tame affair, although Mpenza gave United a scare when he headed just off target.
City were offering more of a physical threat than a footballing one and Nemanja Vidic needed treatment after a late challenge by substitute Paul Dickov.
And yet Stuart Pearce's side were thrown a lifeline with 11 minutes left when Ball tumbled under Brown's challenge.
But in keeping with their hapless record in front of goal, Vassell blasted the spot-kick straight at Van der Sar's legs.
United held in on comfort - and the celebrations at the final whistle suggested Ferguson's side know the title is theirs, barring a Chelsea miracle.
Man City: Isaksson, Onuoha, Dunne, Distin, Ball, Hamann (Jihai 46), Vassell, Johnson, Ireland (Dickov 69), Beasley (Sinclair 61), Mpenza.
Subs Not Used: Weaver, Samaras.
Booked: Johnson, Dickov.
Man Utd: Van der Sar, Brown, Ferdinand, Vidic, Heinze, Ronaldo, Carrick, Scholes, Giggs, Smith (Fletcher 73), Rooney (O'Shea 87).
Subs Not Used: Kuszczak, Solskjaer, Richardson.
Booked: Van der Sar, Giggs.
Goals: Ronaldo 34 pen.
Att: 47,244 Ref: R Styles (Hampshire).