By Martyn Herman

Manchester United surged nine points clear at the top of the Premier League with an edgy 3-1 derby victory over Manchester City on Saturday.

City had not won a league game at Old Trafford since 1974 and their hopes of ending that depressing sequence were dashed as Wayne Rooney and Louis Saha struck before halftime.

Hatem Trabelsi pulled a goal back for City with 18 minutes remaining, but Cristiano Ronaldo eased United's jitters when he tucked in a late third.

United, who have 44 points from 17 games, now hold their biggest lead in a title race since 2001, although Chelsea can close the gap to six points with victory over Arsenal on Sunday.

"There are a lot of hurdles to navigate but I don't see any reason why we can't do it," manager Alex Ferguson told Sky Sports. "With us playing before Chelsea we can relax now and watch the game tomorrow and support the Gunners!"

Portsmouth moved third on 28 points after a 2-0 home victory over Everton with Nwankwo Kanu's ninth goal of the season adding to a sensational 40-metre volley from Matthew Taylor. Kanu is now top of the Premier League scoring charts.

Steven Gerrard put Liverpool on the way to a second successive 4-0 league victory and fourth place. Jamie Carragher, Luis Garcia and Mark Gonzalez were also on target with all the goals coming in the second half.

Bulgarian striker Dimitar Berbatov's double helped Tottenham Hotspur to a 5-1 rout of lowly Charlton Athletic, their ninth home victory in succession in all competitions.

Watford are still propping up the table after their eighth draw of the season, 0-0 at home to Reading.

The Manchester derby proved an eventful encounter and maintained United's long unbeaten league run which stretches back to September.

CHEAP GOALS

Stuart Pearce had not tasted defeat at Old Trafford since taking over as City boss, but the former England hard man blamed "cheap goals" for ending that record.

All three United goals were down to defensive mistakes, beginning in the fifth minute when Ronaldo's low cross was not dealt with and Rooney swept in his 50th Premier League goal.

City had their moments, most notably when teenage fullback Micah Richards headed narrowly wide after indecision in the United defence and Georgios Samaras stung Edwin van der Sar's fingers with a volley.

Seconds before halftime, however, Trabelsi lost possession in the corner, allowing Gabriel Heinze to fire in a cross shot that Saha touched past Nicky Weaver in the City goal.

Weaver failed to return for the second half after being injured trying to deny Saha, and he was replaced by Sweden international Andreas Isaksson.

Trabelsi made up for his error after 72 minutes, surprising Van der Sar with a curling shot that cannoned in off the underside of the crossbar.

"I told the boys at halftime that if we could get a goal back there would be some nervous times around Old Trafford," Pearce told Sky Sports.

"We got the goal back but we weren't strong enough to really get after them and if we had been we could have got back to 2-2 and maybe gone on to win it."

Instead, another missed interception from Richard Dunne six minutes from time allowed Ronaldo to seal the points, shortly before City's Bernardo Corradi was sent off for a blatant dive.

"It was a typical derby game. You have to earn the right to win these matches and we did that. It was a great result," said Ferguson.

Elsewhere, Newcastle United's improvement continued as Obafemi Martins scored twice in a 3-1 victory at Blackburn Rovers, who had Stephane Henchoz sent off before halftime.

Middlesbrough came from behind to grab a point in a 1-1 draw at home to Wigan Athletic who had goalkeeper Chris Kirkland taken to hospital with a head injury.

"He went into delayed shock at halftime," Wigan boss Paul Jewell told the BBC. "Thankfully he appears to be okay."