Members of Pakistan's spy agency are pressing Taliban field commanders to fight the U.S. and its allies in Afghanistan, some U.S. officials and Afghan militants say, a development that undercuts a key element of the Pentagon's strategy for ending the war.

The explosive accusation is the strongest yet in a series of U.S. criticisms of Pakistan, and shows a deteriorating relationship with an essential ally in the Afghan campaign. The U.S. has provided billions of dollars in military and development aid to Pakistan for its support.

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