KABUL, Afghanistan — The training of Afghan Local Police and special operations forces has been put on hold while their American trainers conduct stricter vetting to try to root out any infiltrators or new recruits who could pose risks to the coalition troops working with them, American officials say.

The move does not affect the vast majority of Afghan forces — more than 350,000 Afghan National Army soldiers and Afghan National Police members — who are still being trained and are still working in the field with American and NATO counterparts, military officials said. The action was first reported online by The Washington Post.

“The training is definitely still going on for the regular A.N.A. and A.N.P.,” said Maj. Steve Neta of the Canadian Air Force, a spokesman for the NATO training mission in Afghanistan. At any given time, there are 25,000 Afghan soldiers and more than 4,000 Afghan national policemen in training, and that is continuing, he said.

But a rash of recent attacks by Afghan forces on American and NATO troops has led American Special Operations commanders in Afghanistan to put a hold on the training of those Afghan units overseen by American Special Operations forces: Afghan Local Police and special forces units, which, combined, number over 20,000, or roughly seven percent of all Afghan forces.