Thomas Vermaelen's dramatic added-time winner moved Arsenal to within one point of third-placed Tottenham Hotspur after a 2-1 victory over Newcastle United at the Emirates Stadium on Monday.
Arsene Wenger's side looked as though they would stumble in their efforts to increase the pressure on their near neighbours as the visitors hung on stubbornly until the dying moments.
Robin van Persie had scored his 33rd goal of the season a minute after Hatem Ben Arfa had given the visitors a 14th minute lead.
But Arsenal were forced to wait until the final moments of the game before Vermaelen finished off a superb attacking move by sweeping the ball home past Tim Krul to secure a fifth successive league victory for the home side.
Newcastle remain in sixth position but with an eight-point gap not separating them from Arsenal, their hopes of a top four finish have effectively been ended.
Back to back victories over close rivals Tottenham and Liverpool had revitalised Arsenal's Premier League campaign.
And while they narrowly failed to overturn a four-goal deficit from the first leg of their Champions League clash with AC Milan, the 3-0 second leg victory had only strengthened the Gunners' growing confidence.
They could take nothing for granted, however, against an improving Newcastle side and the visitors confirmed their threat after just 14 minutes when they took the lead through Ben Arfa.
Vermaelen was guilty of a lapse in concentration when he gave the ball away needlessly in the centre of the field.
The ball was moved out to Ben Arfa on the right flank and Vermaelen's error was compounded by keeper Wojciech Szczesny who allowed the winger's left foot shot to beat him at the near post.
Arsenal were stunned but there was little time for home frustration to set in with Van Persie replying within 60 seconds of Newcastle taking the lead.
The striker had already missed an open goal in the third minute when he failed to connect with Theo Walcott's low right wing cross that eluded visiting keeper Tim Krul.
But he made amends with a much harder finish with Walcott once again in the role of provider.
Van Persie collected his team-mate's cross with a superb first touch that took him away from the challenge of centre back Mike Williamson before placing his shot beyond Krul.
The Holland striker is brimming with confidence and his powerful free kick shortly after his goal illustrated his belief.
But Van Persie alone could not see off a determined Newcastle side and the visitors responded impressively, taking control of the game during the final stages of the first half without managing to threaten Szczesny's goal.
Arsenal clearly needed to assert themselves on the game if they were to avoid dropping valuable home points.
And the way they started the second half suggested Wenger had made his feelings known at half time.
Four minutes after the restart Walcott again delivered a telling cross from the right, this time towards Tomas Rosicky whose glancing header was saved by Krul.
The pair combined again later midway through the half with Rosicky -- who agreed a new two-year contract to stay at the club earlier in the day -- this time slicing a left foot effort wide.
And in between, Mikel Arteta had found Van Persie but Krul again reacted well to save.
Newcastle had effectively faded as an attacking force with Arsenal spending long periods in the opposition half.
Wenger introduced Gervinho and Aaron Ramsey as second half substitutes in a bid to freshen up his side's attacking options against the tenacious approach of Newcastle's midfield and back four.
Arsenal's efforts grew more frantic but in the fifth minute of extra time Walcott once more turned provider, crossing from the right and the ball was deflected into the path off Vermaelen who finished right footed from close range.