The Premiership leaders failed to reproduce anything like the form they had displayed in their three previous matches in group F and, despite generating enough chances to have won fairly comfortably, could have few complaints about going down to Marcus Allback's 73rd-minute strike.

With nine points already in the bag, United remain favourites to top the group but the battle for second place is now wide open between the Danes, Celtic and Benfica.

The Dane's coach Stale Solbakken said: "It is a great, great achievement and I am really proud to be FC Copenhagen's coach on a night like this."

Ferguson had arrived in Copenhagen pledging to field the strongest team available to him.

If that was his intention, the injury-friendly combination of the inhospitable weather and a potato field of a pitch must have persuaded him otherwise.

Both Rio Ferdinand and Paul Scholes were left on the bench at the start, allowing Mikael Silvestre a rare start in the centre of defence and Michael Carrick the opportunity to play a more adventurous role in midfield.

With Ryan Giggs, Gary Neville and Louis Saha all back in Manchester nursing injuries, barely half of United's current first-choice line-up was on display in the Parken stadium.

Among those not afforded a night off was Wayne Rooney, and it was the England striker who came closest to breaking the deadlock in a scrappy first half.

After swivelling on Gabriel Heinze's pass on the edge of the area, he thumped a 13th-minute drive into the arms of Jesper Christiansen before heading Wes Brown's cross from the right narrowly over the Copenhagen goalkeeper's crossbar.

For all their bustling, the Danes initially posed little in the way of a genuine threat to United's makeshift defensive quartet. Michael Silberbauer's 20-yard strike was their only effort to find the target before the break and was never likely to squeeze past van der Sar at his near post.

Copenhagen's problems in keeping tabs on Rooney were underlined when centreback Brede Hangeland was booked for a clumsy hack at the 21-year-old, who saw another shot trickle wide of the target just before the interval after he had turned his marker on the penalty spot.

With Ferdinand replacing Nemanja Vidic at the break, United might easily have found themselves behind in the first ten minutes of the second period.

Unchallenged at the back post, Hangeland nodded Lars Jacobsen's corner straight at van der Sar and Atiba Hutchinson failed to even hit the target with an even more inviting cross from Silberbauer after the midfielder had wriggled clear of Wes Brown on the left.

At the other end, Christiansen twice thwarted Ole Gunnar Solskjaer, diving at the Norwegian's feet after he had been played in by Cristiano Ronaldo then getting down smartly to smother a shot on the turn.

Another United chance went begging when Rooney headed Heinze's deep cross wide of Christiansen's right-hand post mid-way through the half.

Solskjaer then ran on to a Rooney flick and fired in a left-foot effort from the edge of the area that was deflected inches wide of the opposite post.

United were made to pay for those near misses when Copen-hagen won a 73rd-minute corner.

Swung in from the right, the ball fell beyond the back post to Michael Gravgaard whose return cross was headed towards goal by Hutchison and then stabbed over the line by Allback.

Christiansen had to make one more good stop to deny Ronaldo but the Danes held out for a win that keeps alive their chance of making a first appearance in the knockout stages of the competition.

Solbokken said he was proud of his men.

"My players ran and fought as much as they did for the whole game. Some of them could barely walk in the last ten minutes but still we managed to keep it tight after we scored.

"But of course we must admit they had more chances than us and we rode our luck a little bit but it is a good feeling for the lads."
WEDNESDAY'S RESULTS
GROUP E
Lyon (FRA) 1 (Benzema 14) Dynamo Kiev (UKR) 0
Real Madrid (ESP) 1 (Nicolita 70-og) Steaua Bucharest (ROM) 0
GROUP F
Benfica (POR) 3 (Caldwell 10-og, Gomes 22, Karyaka 76) Celtic (SCO) 0
FC Copenhagen (DEN) 1 (Allback 73) Manchester United (ENG) 0
GROUP G
Arsenal (ENG) 0 CSKA Moscow (RUS) 0
SV Hamburg (GER) 1 (van der Vaart 62) FC Porto (POR) 3 (Lucho Gonzalez 44, Lisandro Lopez 61, Moraes 87)
GROUP H
AC Milan (ITA) 4 (Kaka 7-pen, 22, 56, Gilardino 88) Anderlecht (BEL) 1 (Juhasz 61)
AEK Athens (GRE) 1 (Liberopoulos 74) Lille (FRA) 0