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 60 percent of the 2,000 allied deaths in the nine-year war. They have also accounted for 30 percent of all Afghan civilian deaths.
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 raising more troops for the war effort, with at least 450 training slots still unfilled after more than a year.
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.
It is not clear exactly where the new troops will come from since 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 official said the new trainers were needed to staff new schools for combat support and service support specialties to enable the transition of responsibility to the Afghan forces.
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.
Another NATO official, who also asked not to be named for the same reason, said the renewed request for more trainers and explosives disposal experts was part of a routine review of force requirements.
"There is an ongoing discussion on possible additional resources needed to continue supporting the efforts under way," she said.
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 The Dutch have already withdrawn their contingent from southern Afghanistan and the Canadians have said they would follow suit.