West Ham manager Sam Allardyce believes his side were denied a "famous victory" over Premier League leaders Manchester United after Robin van Persie scored a late equaliser from an offside position.
The Hammers had twice taken the lead in the game courtesy of goals from Ricardo Vaz Te and Mohamed Diame.
Antonio Valencia had once levelled for United before van Persie's goal 17 minutes from time.
The Dutchman reacted quickest to the loose ball after Shinji Kagawa's effort hit the post but he appeared offside, although assistant referee Harry Lennard failed to raise his flag.
That decision left Allardyce deflated at the fact his side were unable to record a stand-out victory over the champions elect.
"I think it is a big decision that has possibly taken the famous victory away from us," he said.
"To play as well as we did today and score the types of goals we scored - when you see it is an offside goal that is bitterly disappointing.
"At the end of the day it is a terrific performance by the players and it is fantastic in terms of how they have played at home all season.
"It is another precious point against the team who are going to be the new Barclays Premier League champions."
Allardyce admitted he would have taken a draw ahead of the match but suggested in the aftermath of the result that the level of officiating was not up to scratch.
He said: "I would have settled for a point before the start of the game and I'm very, very pleased by the performance of the players and I hope they can keep it up between now and the end of the season.
"This level of football has to be equalled by the level of the officials who are in charge of the game.
"His [Lennard's] coaches have to coach him properly and coach him into getting better (positions) - that is why they are professional these days.
"They need coaching on the good decisions, with a pat on the back, but also they need coaching on when they haven't made the right call.
"It is a major decision that has gone against us. In the end we have gained a point - this highlights again just how good we are here at Upton Park."
The salvaged draw for United means they are now four points away from claiming their 20th league title and Sir Alex Ferguson was delighted with the fighting qualities of his side.
"We had to stand up to a lot, we went down twice but we kept going. We played like champions tonight," he told Sky Sports 2.
"It was magnificent in terms of determination and courage to play. It's one more game away - we're determined to win, we don't like losing and they showed that tonight again."
One area of contention for Ferguson was a challenge on goalkeeper David De Gea on the stroke of half-time.
Andy Carroll, fresh from a tangle with Wayne Rooney and a talking to from referee Lee Probert, crashed into De Gea as he launched himself towards a set-piece and Ferguson felt the on-loan Liverpool forward should have been dismissed for the challenge.
"I think it's obvious," he added. "I don't think we need to dwell on that, it's an obvious red card but the referee has seen it differently.
"We know how they play, the ball is in the air most of the time. You've got to defend those things and they're very, very aggressive so you hope there's a strong referee. I'm not so sure we got that tonight."