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Currently there are 8,400 US troops in Afghanistan

Washington (CNN) Gen. John Nicholson, commander of US forces in Afghanistan, said Thursday that the coalition faced "a shortfall of a few thousand" troops to break the "stalemate" it faces there.

He said troops were needed for the NATO-led train, advise and assist mission in Afghanistan. He said that the resources for the counterterrorism mission there, in contrast, are "adequate."

Nicholson, testifying before a Senate Armed Services Committee hearing on Afghanistan, said the shortfall could be made up by US or coalition troops. He added that Secretary of Defense James Mattis would address the issue during this month's meeting of NATO defense ministers in Brussels.

Currently there are a total of 8,400 US troops in Afghanistan. There are also 6,000 troops from NATO and other allied countries. President Barack Obama oversaw the withdrawal of some 1,400 US troops during his last months in office.

Nicholson said he hoped the additional reinforcements would allow the coalition to advise Afghan troops at the brigade level, bringing them closer to the intense fight between the government and Taliban insurgency.

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