A controversial penalty helped Wayne Rooney cancel out Fernando Torres's early opener before Ji-Sung Park headed a second-half winner.

The result leaves Liverpool four points behind fourth-placed Tottenham, who have a game in hand.

The Reds, whose only change was Maxi Rodriguez in for Ryan Babel, had got off to a dream start on five minutes when Torres back-heeled to Gerrard, who in turn found Dirk Kuyt down the right.

The Dutchman crossed into the six-yard box, where Liverpool's No.9 had peeled off Gary Neville ready to power a header beyond Edwin van der Sar.

The travelling Kop had barely finished bouncing, however, when Howard Webb awarded United a penalty following Javier Mascherano's tug on Antonio Valencia. Replays clearly showed contact was first made outside the box, but Rooney kept his cool amid Liverpool protests to fire in the rebound after Pepe Reina's initial save.

The incident prompted a heated exchange on the touchline between Messrs Benitez and Ferguson, with the former's anger at the penalty decision matched by the latter's disdain at Mascherano only receiving yellow for denying a goalscoring opportunity.

A period of relative calm ensued until the 29^th minute when Nani forced an outstretched save from Pepe Reina with a right-foot drive from distance.

Park headed narrowly wide from Patrice Evra's cross on 40 minutes but the game was struggling to live up to the excitement of the opening minutes.

United started the second period on the front foot when Nani got the better of Glen Johnson only to be halted by a determined Jamie Carragher.

The lively Park was next to threaten when he drove at Carragher and Daniel Agger before rifling his shot into the arms of Reina.

The South Korean had been United's best player on the day and it was he who gave the hosts a 2-1 lead on 60 minutes by ghosting past Johnson at the far post and nodding home Darren Fletcher's cross.

There followed a break in play while Rodriguez received treatment after a kick in the head from Neville.

Benitez threw on Babel and Alberto Aquilani with just under 20 minutes remaining but it was United who almost scored next when Rooney turned Agger before dragging wide of Reina's goal.

At the other end Torres and substitute Yossi Benayoun both fluffed late efforts from Gerrard's square ball across goal.