Forlan was thrilled to grab the winner

Diego Forlan's injury-time winner kept Manchester United at the heart of the title race and left Chelsea stunned at Old Trafford.

Subsitute Forlan decided a game that looked destined for stalemate with a powerful strike in the third minute of stoppage time after a superb through-ball by Juan Sebastian Veron.

We are right behind Arsenal now and if we keep knocking on the door, hopefully it will open Sir Alex Ferguson Full match reaction

The victory kept the pressure on Premiership pace-setters Arsenal, but was heartbreaking for Chelsea, who looked on course for a hard-earned point.

Eidur Gudjohnsen gave Claudio Ranieri's side the lead on the half-hour, but Carlo Cudicini's mistake allowed David Beckham to set up Paul Scholes' equaliser within eight minutes.

Forlan then stepped into the hero's role to snatch a dramatic victory.

Ferguson left Ryan Giggs and Veron on the bench, while Chelsea left Gianfranco Zola on the bench and restored Gudjohnsen alongside Jimmy Floyd Hasselbaink.

It was a surprisingly lacklustre opening half from United - and they could count themselves fortunate to go in level at the interval.

Chelsea were in comfortable control, despite losing Hasselbaink inside 20 minutes with an ankle injury sustained in a challenge with Phil Neville.

He attempted to carry on, but was swiftly replaced by Zola.

Gudjohnsen grabbed a fine opener

United were rarely a threat, but had penalty appeals rejected after 21 minutes when Beckham's cross struck Celestine Babyaro on the arm.

Chelsea deservedly took the lead on the half hour, when Emmanuel Petit released Gudjohnsen, who flicked a delicate finish beyond Fabien Barthez.

The lead last only eight minutes as United restored equality after a moment of rare carelessness from Cudicini.

He sent a clearance straight to Beckham, and his trademark cross was met by Scholes' header.

It was harsh on Chelsea, and Ferguson reflected his discontent by sending on Giggs for Phil Neville at the start of the second half.

The fight is between Arsenal and Manchester United now Chelsea coach Claudio Ranieri Full match reaction

The move galvanised United - and they only narrowly missed taking the lead early in the second half.

Ole Gunnar Solskjaer struck an upright from eight yards after Beckham's short corner - then Jesper Gronkjaer blocked Scholes' goalbound shot.

Chelsea were still dangerous and Barthez needed to be alert to block Gudjohnsen's drive.

Cudicini denied van Nistelrooy but could not stop Forlan

Cudicini made amends for his earlier error with a moment of brilliance after 70 minutes.

Ruud van Nistelrooy's header looked destined for the bottom corner until the Italian dived brilliantly to his right to save.

It was the Dutch striker's last contribution as he was replaced by Forlan.

And Forlan almost marked his arrival with a goal within three minutes, Cudicini again saving well from 20 yards.

United had been a side transformed after the break, and Roy Keane was guilty of wasting an golden chance 10 minutes from the end when he shot wide from close range.

But Forlan was not to be denied, repeating his Worthington Cup heroics against the same opponents.

Man Utd: Barthez, Gary Neville, Ferdinand, Brown, Silvestre (Veron 85), Beckham, Keane, Scholes, Phil Neville (Giggs 45), van Nistelrooy (Forlan 71), Solskjaer.
Subs Not Used: Carroll, O'Shea.

Chelsea: Cudicini, Gallas, Melchiot, Desailly, Le Saux, Gronkjaer (De Lucas 56), Petit, Lampard, Babayaro, Hasselbaink (Zola 16), Gudjohnsen (Zenden 84).
Subs Not Used: de Goey, Morris.

Attendance: 67,606

Referee: P Durkin (Dorset).