Champions show their class as misfiring Gunners are humbled in title-race showdown.
Arsenal 1 - 3 Manchester United : Rooney the destroyer - Sharpshooter Wayne shatters Gunners' title illusions with a little help from Nani
Manchester United swept aside title rivals Arsenal 3-1 at Emirates Stadium to move a point behind leaders Chelsea.
Nani opened the scoring in the 33rd minute when his chip across goal was palmed in by Arsenal goalkeeper Manuel Almunia, before in-form England striker Wayne Rooney swept home a second following a quick counter attack.
A third on the break from Ji-sung Park at the start of the second half effectively ended the contest, although defender Thomas Vermaelen netted a consolation for the out-muscled Gunners.
Nani described the match as his best performance since joining United from Sporting Lisbon in 2007.
'I think that was my best game,' said the Portugal international. 'I played well, scoring and getting an assist.
'It was a fantastic performance from the team and I was so happy to help. I'm working hard every day to be fit for the team.
'I want to help the team play well. I can feel the confidence of my team-mates, the fans and the manager. I'm so happy and want to continue this good form.
'We had a very good game (against Manchester City) last Wednesday and that gave everyone confidence for this match.
'The manager said we had to have the same attitude today if we want to be champions.'
Arsenal, who had started the match five points behind Chelsea ahead of their trip to Stamford Bridge next weekend, began well as Andrey Arshavin got away down the left, before cutting inside and trying to curl the ball past Edwin van der Sar from a tight angle, but his shot drifted wide.
CATCH ME IF YOU CAN ... Paul Scholes chases Nani after Manuel Almunia pushed in the winger's cross
United, though, were quick to regain possession and then cut down any space for the home side. Nani and Darren Fletcher combined as they almost played in Rooney, but William Gallas made an important blocking tackle in the six-yard box.
Alex Song - back from the African Nations Cup - then had to hack the ball clear at the far post as United again got clear down the right far too easily.
When Arshavin - who was ineligible for last season's Champions League semi-final clash between the sides - burst away again, he lacked any support in the middle.
The Russian, though, remained Arsenal's most potent attacking threat.
In the 13th minute he skipped away down the left, cut back inside Wes Brown and curled another effort goalwards, which this time was only just wide of the far post.
Arsenal captain Cesc Fabregas suddenly burst into life with a surging run down the middle, before slipping in Arshavin, but the Russian lost his footing at the key moment and United cleared.
United - who have played a match more than Chelsea - slowly started to gain the upper hand and Gallas needed to make another timely tackle in the penalty area as Paul Scholes shaped to shot.
Nani drilled the ball wide as Arsenal were again exposed in the right channel, before playing a key part in the goal which gave United the lead.
The winger skipped easily in between two defenders then chipping the ball back across goal. Almunia pushed it inside his far post, with Park Ji-Sung ready to tap the ball into the net.
Wayne Rooney connects with a cross from Nani to volley in Manchester United's second goal after 37 minutes.
Wayne's world: Rooney celebrates
Fabregas' shot following a corner was blocked - and four minutes later United were 2-0 ahead. Again Nani was the provider, dashing clear after picking the ball up from Rooney before squaring it for the England striker to sweep home his 22nd goal of the season, low into the corner.
The Gunners faced an uphill battle to get back into the match, with Arshavin firing wide from just inside the box - as manager Arsene Wenger was left to scratch his head and looked to the heavens for inspiration.
It could have been worse on 41 minutes, but Nani blazed his shot wide after more good work from Rooney down the left.
There was a hold-up at the start of the second half as Rooney received treatment following a knock on the knee in a challenge with Bacary Sagna.
The England forward, though, was soon back in the action, and tested Almunia with a fierce angled drive after cutting in from the left.
It was game over on 52 minutes, when United scored a third following another simple counter.
This time is was Park who broke clear, sprinting onto Fletcher's chip into the Arsenal half and then slotting past Almunia from just inside the box.
Walk in the Park: South Korea star Ji-sung Park celebrates United's third
The Gunners were also well beaten here 3-0 by Chelsea at the end of November, before a run of seven wins from nine hauled them back into title contention.
Fabregas, continued to drive his young team on, firing over and then just too close to van der Sar, then Song volleyed wide.
Theo Walcott came on as substitute - and Arsenal pulled a goal back with 11 minutes to go when Vermaelen's volley took a deflection off Jonny Evans to wrong-foot van der Sar.
However, there was to be no grand finale as Wenger's youngsters were again found wanting when it mattered most.
Arsenal manager made to regret pre-match boast as he blames naïvety and individual errors for defeat against Man United.
Arsenal: Almunia, Sagna (Bendtner 72), Gallas, Vermaelen, Clichy, Fabregas, Song, Denilson (Walcott 61), Nasri, Arshavin, Rosicky (Eboue 71). Subs not used: Fabianski, Ramsey, Silvestre, Traore. Booked: Song.
Goals: Vermaelen 80.
Man Utd: Van der Sar, Rafael Da Silva, Jonathan Evans, Brown, Evra, Scholes (Giggs 71), Carrick, Fletcher, Nani (Berbatov 89), Rooney, Park (Valencia 87). Subs not used: Kuszczak, Owen, Gibson, De Laet.
Goals: Almunia 33 og, Rooney 37, Park 52.
Att: 60,091
Ref: Chris Foy (Merseyside).
