David Silva scored the only goal as Manchester City marked Roberto Mancini's second anniversary in charge by staying top of the Premier League with a 1-0 victory over Arsenal on Sunday.
Mancini's big-spending side had provisionally gone behind on points after Manchester United's 2-0 victory at Queens Park Rangers earlier in the day.
But Spain international Silva's fifth league goal of the season - and City's 50th - proved decisive with a 53rd minute close range finish.
City has a two-point lead over United after 16 games. However, Mancini warned his players they still have much to do to take the title from defending champion United.
''We can't think that we can win the title without a fight from United, it's impossible,'' the City manager said.
The result was the perfect response from City after its unbeaten league start to the season was ended by Chelsea 2-1 last week.
''We are delighted because after losing to Chelsea it was really important to beat Arsenal,'' Mancini said.
The result leaves Arsenal 12 points adrift of City and manager Arsene Wenger believes his team's hopes of winning the title may have gone.
''It will be difficult to close the gap on City now, but we will try,'' Wenger said. ''This was a game we couldn't afford to lose. It's difficult to take but we will continue to fight.''
Robin van Persie, Aaron Ramsey and Thomas Vermaelen went close for Arsenal while City's Pablo Zabaleta was denied by a post from 25-yards (meters) in the 66th minute.
Arsenal made its first return to the city after a humiliating 8-2 defeat against City's neighbours Manchester United at Old Trafford on Aug. 28.
Wenger's side had recovered well from that disaster, winning nine out of 12 league games to arrive at the Etihad Stadium back in contention for a top-four berth.
The stage was set for a compelling contest between two of the Premier League's top heavyweights.
City, bankrolled by billionaire Abu Dhabi owners, named former Arsenal players Kolo Toure and Samir Nasri in their side. Yet in Robin van Persie, the visitors possessed the most in-form striker in the Premier League after scoring 12 times in his previous eight league outings.
In a tight but entertaining clash, there was nothing to separate the clubs at half time.
Sergio Aguero and Silva teased and tormented Arsenal's back four but it was City's Joe Hart who was the busier of the two goalkeepers in the opening 20 minutes.
England goalkeeper Hart was forced to save from Gervinho, Aaron Ramsey and defender Vermaelen all in the space of 60 dramatic seconds before his opposite number Wojciech Szczesny denied Mario Balotelli from close range following a 23rd minute cross by Micah Richards.
Both teams looked capable of winning the game.
Van Persie was quiet in the opening half an hour before the Netherlands striker flashed a 32nd minute header narrowly wide from 12 yards before Silva broke the deadlock seven minutes into the second half.
The former Valencia player showed lightning reactions to hook the ball over the line after Szczesny was unable to hold Mario Balotelli's powerful shot after the Italian had been allowed to cut inside the Arsenal area.
It was City's 50th Premier League goal of the season - 25 at home, 25 away - but Arsenal responded through Theo Walcott and Van Persie being denied by Hart's fine saves.
Then City full-back Zabaleta rattled the Arsenal post from 25 yards in the 66th minute before the hosts survived late scares with Vermaelen twice going close before the end of a breathtaking game.
