Wojciech Szczesny of Arsenal saves a shot from Wayne Rooney of Manchester United during their English Premier League match at the Emirates stadium in north London on Sunday. Arsenal won 1-0. Eddie Keogh / Reuters

Sir Alex Ferguson insists Manchester United paid the price for a refereeing error in the 1-0 defeat at Arsenal as the Premier League title race was blown wide open.

Ferguson believes referee Chris Foy got it wrong when he failed to award an 88th minute penalty following Gael Clichy's clumsy challenge on Michael Owen.

The United manager acknowledged Arsenal had a good claim for a spot-kick turned down when Nemanja Vidic handled Theo Walcott's cross in the first half.

But having seen Chelsea close the gap at the top to three points 24 hours earlier after benefiting from two dubious decisions in a 2-1 victory over Tottenham, Ferguson attempted to set the agenda ahead of the Blues' decisive trip to Old Trafford on May 8.

The title race swung Chelsea's way 11 months ago when Didier Drogba scored the winning goal despite being in an offside position in the corresponding fixture and Ferguson is anxious to avoid a repeat.

"It's too big a game not to get the decisions right," Ferguson said. "It balances out in that respect but I think it was difficult to see that one (Vidic's handball) but the one at the end, Clichy knew, he put his hands up in horror.

"Obviously, it gives Chelsea a major chance now and that's what happens when you get these decisions. They (Chelsea) got one at Old Trafford last season so that's the worry now.

"But in terms of ability - a game at Old Trafford, the supporters will be ready for it - and so will our players."

Aaron Ramsey struck in the 56th minute to cap a period of Arsenal dominance and Ferguson admitted his side only found anything like its normal form in the final stages of the game.

"After that we dominated and I think we deserved something," he said. "I think we didn't use the ball properly but once we lost the goal we were in their half most of the time."

Arsenal now lies six points off the top with three games remaining and manager Arsene Wenger refuses to call time on the club's ambitions of being crowned champion.

Its chances will be improved if Chelsea beats United and Wenger admitted he would be backing Carlo Ancelotti's side when the top two meet.

"I have not given up all hope because we will fight until the last second of the season," he said.

"We have been unlucky this season. Let's hope we have better luck in the last three weeks. The best position remains Manchester United and second best is Chelsea because they have to play United next week.

"I still make United strong favorites because when you play at home for the title you have still an advantage.

"If we want to have a small chance it is in our interests for Chelsea to win and for us to win our games. Then it's mathematically possible. But I still say United has the advantage."

Wenger admitted his side's recent failings were still likely to prove costly and he pin-pointed its previous three games as the moments when its bid faltered.

"Last week, at Bolton, against Liverpool when we were 1-0 up in the 97th minute and we were 3-1 up against Tottenham," he said.

"If we do not win the championship, we could have made nine points from these games and we would have been ahead of United."

Samir Nasri came off at halftime with a hamstring strain while Cesc Fabregas missed the game with a thigh problem but both should be available to face Stoke next weekend.