Manchester United manager Alex Ferguson is urging his players to seize the chance to open up a six-point lead over champions Chelsea at the top of the Premier League when the title contenders clash on Sunday.

"You can't hide the fact that it is a fantastic prospect of a match. It's a great opportunity for us," Ferguson told a news conference on Friday ahead the Old Trafford battle. "I don't think there's any way I can look at it otherwise. I think my players and the supporters should be looking at it that way."

Ferguson's side have never previously led Chelsea at this stage of the season since Jose Mourinho took charge of the Londoners in June 2004. Ferguson is determined to press home the advantage as United look to end a four year wait for the title.

"I don't think it's lost the fact that in the last two years Chelsea have been in the fantastic position of being nine, 10 points ahead of us and very difficult to peg back," he said. "We did our best last year in terms of coming with a later run but it was not quick enough.

"We have got out of the blocks this time and for the first time we are in front and with the prospect of maybe going six points clear, which would have them chasing us, rather than us chasing them."

United, who like Chelsea lost 1-0 away in the Champions League in midweek, have no fresh injuries for a game that will be under massive scrutiny.

Howard Webb has been selected as the referee and Ferguson wants him to be left alone to do his job. "I hope it's not a game like we've seen recently. We don't want to see players crowding round referees," Ferguson said.

"We want to let them get on with the game and give him a chance. He's a young referee and I think if he's fair no-one can complain."