Man City held in blow to Premier League title bid
Pep Guardiola's side took the lead through Bernardo Silva's first-half goal, but Konstantinos Mavropanos hauled West Ham level before the interval at the London Stadium.
Just hours after Arsenal scored twice in the final minutes against Everton to seal a priceless 2-0 victory, second-placed City cracked under the pressure of trying to keep pace with the Gunners.
City have a game in hand on Arsenal but they look destined to miss out in a title race that could turn into a procession long before the finish line.
Draws in their last two league matches against relegation-threatened West Ham and Nottingham Forest have exposed the flaws in a City team expensively rebuilt by Guardiola with limited success over the last 18 months.
They will have to improve significantly to have any hope of a miraculous recovery from 3-0 down against Real Madrid in the Champions League last-16 second leg on Tuesday.
Guardiola's men then head to Wembley to face Arsenal in the League Cup final before meeting Liverpool in the FA Cup quarter-finals.
As if that wasn't problematic enough for spluttering City, their next two league games after the three cup matches are against Chelsea and Arsenal.
By the end of that five-game gauntlet, City could be facing up to the painful prospect of a second successive season without major silverware.
West Ham are out of the relegation zone for the first time in 100 days -- one point ahead of Forest, who play their game in hand against Fulham on Sunday.
Ruthlessly exposed by Real in midweek, the defensive weaknesses that have plagued City this season are combining with Erling Haaland's barren spell to leave the title challengers bereft at both ends of the pitch.
Impotent City
Haaland has only scored three times in his last 12 league games and the Norway striker was largely anonymous once again.
Guardiola moaned that he had been "massacred" by critics for his team selection against Real.
Once again, his tactics were worthy of debate as City monopolised possession for long periods, but did little to threaten West Ham despite starting with Haaland and Omar Marmoush up front.
When City finally pieced together a threatening raid, they immediately carved open the West Ham defence to take the lead in the 31st minute.
Silva made a dangerous run down the left edge of the West Ham penalty area, but he got a huge stroke of luck as his miscued cross towards Haaland caught goalkeeper Mads Hermansen by surprise as it looped in at the far post.
Silva's sheepish expression told its own story but the Portugal midfielder wasn't about to complain after scoring for just the second time in the league this season.
Yet City's lead lasted just four minutes as Gianluigi Donnarumma's blunder gifted West Ham their equaliser.
The City 'keeper should have claimed Jarrod Bowen's corner but he completely misjudged the delivery and was punished by Mavropanos, who headed home from close range via the underside of the crossbar.
Antoine Semenyo wasted a golden opportunity to restore City's lead before half-time, shooting wide after Haaland pounced on Aaron Wan-Bissaka's mistake.
Watching from the stands as he served a touchline ban, Guardiola was in contact with assistant Pep Lijnders by phone, the pair introducing Rayan Cherki and Jeremy Doku in a desperate bid to turn the tide.
Cherki immediately sent Haaland through for a low strike that Hermansen pushed around the post.
Haaland made a hash of finishing Doku's pass with a scuffed effort and Cherki's free-kick clipped the bar.
But City looked increasingly impotent before Marc Guehi blazed over in stoppage-time as their title dreams started to fade.