BRUSSELS — NATO may deploy 2,000 more soldiers to Afghanistan to join the 140,000-strong international force already there, an official said Monday.

Top U.S. and NATO commander Gen. David Petraeus asked for the additional troops, nearly half of whom will be trainers for the rapidly expanding Afghan security forces, said the official, who requested anonymity because he was not authorized to speak on the subject.

Petraeus also asked for troops who know how to neutralize roadside bombs, the cause of a large percentage of the 2,000 allied deaths in the nine-year war.

The request comes ahead of NATO's November summit, where the Afghan conflict will be a major topic of discussion. The alliance has had trouble rising more troops for the war effort, with at least 450 training slots still unfilled after more than a year.

The war is deeply unpopular in many of NATO's 28 member states. In Europe, polls show the majority of voters consider it an unnecessary drain on finances at a time of sharp cuts in public spending and other austerity measures.

The additional trainers are considered the essential element in allied plans to increase Afghanistan's army and police from the present 300,000 members to 400,000 by next year, when the drawdown of international troops is expected to start.

The official said the new trainers were needed to staff new schools for combat support and service support specialties that are seen as essential to enable the transition of responsibility to the Afghan forces.

But NATO officials have said the additional instructors are difficult to come by because none of the member states has large numbers of such specialists available for assignment to Afghanistan.

A number of instructors have been killed in a series of attacks by Afghans against coalition partners, raising fears of Taliban infiltration as the U.S. and its allies speed up the training of Afghan forces.

Several NATO members may start reducing their contingents in Afghanistan after 2011. The Dutch have already withdrawn their contingent from southern Afghanistan and the Canadians have said they would follow suit.