- Saïd Benrahma (33' Pen)
- Jarrod Bowen (54')
- Gabriel Jesus (7')
- Martin Ødegaard (10')
The leaders were 2-0 up and cruising towards restoring their six-point cushion over Manchester City with Gabriel Jesus tapping home in the seventh minute and Martin Odegaard doubling Arsenal's lead with a volley three minutes later.
But everything changed when they conceded a sloppy penalty that Said Benrahma tucked away in the 33rd minute.
West Ham, needing points themselves to stay away from the relegation zone, were transformed although Bukayo Saka had the chance to restore Arsenal's two-goal lead early in the second half only to blaze a penalty well wide.
That miss looked even more costly moments later when Jarrod Bowen volleyed in West Ham's equaliser in the 54th minute.
Just as at Anfield last week when Mikel Arteta's team led 2-0 but ended up hanging on desperately for a 2-2 draw with Liverpool, there was a nervousness about Arsenal's play as the pressure of winning a first title since 2004 intensifies.
City's destiny is now very much in their own hands as Arsenal lead the table with 74 points from 31 games, four more than City who have played a game less and who host Arsenal on April 26.
West Ham, who looked the stronger side after levelling and hit the crossbar through Michail Antonio, have 31 points from 30 games, four ahead of the relegation places.
Arsenal had won all five of their London derbies away from home this season without conceding a goal and had lost only two of the previous 29 league games against West Ham.
That record looked set to continue in a sparkling start but when the full-time whistle sounded Arsenal's players looked crestfallen at losing their grip on the title race.
"Very disappointing. The way we started was superb again, we were in total control, then we lost purpose," Arteta said.
"We gave them hope, conceded a terrible penalty, then credit to them. We got on the rollercoaster where everything is going, corners and throw ins, and we never got away from that."
Arsenal remain in a position that they could have hardly imagined back in August but with City steaming up behind them after collecting 25 points from the last 27 on offer, the odds are shifting towards Pep Guardiola's treble chasers.
It all began so well for Arsenal on a pleasant spring afternoon in east London.
An intricate passing move in the seventh minute ended with Ben White's teeing up Jesus for a tap-in and with West Ham looking dazed and disorganised, unmarked Odegaard then volleyed in Gabriel Martinelli's cross.
West Ham were handed a lifeline when Arsenal midfielder Thomas Partey was caught in possession by Declan Rice and Gabriel then took down Lucas Paqueta and Benrahma coolly beat Aaron Ramsdale from the spot.
Antonio's harsh handball early in the second half, after a VAR check, gave Saka the chance to calm Arsenal's nerves but he made a hash of his penalty.
That turned up the volume from the home fans and less than three minutes after Saka's miss, a lofted ball forward found the impressive Bowen unmarked and he showed great composure to bounce a volley past Ramsdale.
Arsenal still had time to re-group but offered very little in the latter stages and they must now focus on Friday's must-win home clash against bottom club Southampton.
"We have to remember we are still top of the league with everything in our own hands," Odegaard said.
- David Coote
|Brighton & Hove Albion||5||4||0||1||+8||12|
|West Ham United||5||3||1||1||+3||10|