Members of Pakistan's spy agency are pressing Taliban field commanders to fight the U.S. and its allies in Afghanistan, U.S. officials and Afghan militants have told The Wall Street Journal, 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.

The U.S. and Afghanistan have sought to persuade midlevel Taliban commanders to lay down their weapons in exchange for jobs or cash. The most recent Afghan effort at starting a peace process took place this week in Kabul.

But few Taliban have given up the fight, officials say. Some Taliban commanders and U.S. officials say militant leaders are being pressured by officers from Pakistan's Inter-Services Intelligence agency not to surrender.

"The ISI wants to arrest commanders who are not obeying [ISI] orders," said a Taliban commander in Kunar province.

U.S. officials say they have heard similar reports from captured militants and those negotiating to lay down their arms.

A senior Pakistani official dismissed the allegation, insisting Islamabad is fighting militants, not aiding them.

"Whenever anything goes wrong in Afghanistan, ISI is to be blamed," said the senior Pakistani official. "Honestly, they see ISI agents behind every bush in Afghanistan."

The Taliban commander in Kunar, like others interviewed in recent days, said he remained opposed to the presence of foreign troops in Afghanistan and had no plans to stop fighting them. But "the ISI wants us to kill everyone—policemen, soldiers, engineers, teachers, civilians—just to intimidate people," the commander said.

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