MANCHESTER (AFP) - Dimitar Berbatov helped himself to a poacher's double as Manchester United cruised to a 3-0 win over Celtic that leaves the Scottish champions on the verge of Champions League elimination. Wayne Rooney's ninth goal in seven matches for club and country completed what was an almost embarrassingly comfortable victory for the defending champions. The knock that forced Cristiano Ronaldo off ten minutes from the end ensured it was not an altogether positive evening for United but Sir Alex Ferguson's side now know a victory in Glasgow in a fortnight's time will be enough to put them through to the knockout stages with two matches to spare. For Celtic, with just one point from their opening three matches, the chances of survival now look slim after what was their tenth consecutive away defeat in the competition. Celtic boss Gordon Strachan, who described Rooney as "unplayable" in his current form, admitted his side had been well beaten. "Berbatov's two goals were offside but I am not going to sit here and scream about them," he said. "I am a football man and I know when I am beaten, well beaten, so does my team." Ferguson said the win was evidence of the added dimension that Berbatov has brought to his team. "It was fantastic, a marvellous performance again," the Scot said of the Bulgarian's display."He is bringing that composure to the final third of the field. Hopefully the combination is developing with not only Wayne but also Carlos (Tevez)." Ferguson's pre-match suggestion that Ronaldo was in need of a rest did not prevent him from naming the Portugal winger in a starting XI that also featured his international teammate, Nani. With Scott McDonald their only fit first-team forward, Celtic had little option but to opt for a policy of containment with the Australian deployed as a lone striker ahead of a five-man midfield. The ease with which Ronaldo, Berbatov and Rooney were able to escape their markers in the opening exchanges suggested the Scottish champions would struggle to execute their chosen tactics however, and United might have claimed a second-minute lead had an unmarked Anderson connected with Nani's inviting cross from the right. Yet for all the artistry on display in front of him, it was the United goalkeeper, Edwin van der Sar, who had the first saves to make. Having turned away Aidan McGeady's low drive from the edge of the area, the Dutchman produced an even better effort to touch Gary Caldwell's first-time effort over the bar. In between those two incidents there was an indicator of Rooney's current confidence in the acrobatic volley with which he met a Nani cross, only a block from Glenn Loovens denying him a spectacular goal. Ronaldo was left equally frustrated when his 28th-minute strike whistled inches wide of Artur Boruc's left-hand post, but within two minutes United went ahead from a corner on the right. Caldwell failed to clear Nani's delivery decisively and, after O'Shea had prodded the ball back into the six-yard box, Berbatov produced a deft flick with his back to goal to beat Boruc from a position that may have been fractionally offside. That was the cue for United to turn the screw and Celtic's Polish goalkeeper did well to gather Rooney's 30-yard drive at full length. United did have further reason to be grateful to van der Sar when O'Shea sliced a Nakamura freekick towards his own net, but the defending champions should have doubled their lead in first-half stoppage time. Darren Fletcher looked composed as he gathered Rooney's chip and sidestepped Mark Wilson but his strike, which ended high into the stands, was anything but. That miss was rendered insignificant five minutes into the second half when Boruc palmed one of Ronaldo's dipping freekicks back into the centre of his goalmouth instead of helping around the post. Berbatov eagerly accepted the invitation to claim his fifth United goal with a tap-in. It should have been 3-0 minutes later, when Rooney had what television replays suggested was a legitimate goal ruled out for offside. Another opportunity went begging when, with the goal unguarded following Boruc's rash dive at the feet of Berbatov, Rooney clipped a half-volley over the bar. Substitute Carlos Tevez also went close before Rooney finally found the net by collecting the Argentinian's pass and drilling a low drive into the bottom corner from 18 yards out.