ISLAMABAD -- Pakistan's military chief dispatched army troops to the Buner district seized by the Taliban and gave the insurgents 24 hours to pull out, warning they would not be allowed to "impose their way of life" on the nation.

Some Taliban were seen withdrawing Friday, piling into pickup trucks and minibuses with their assault weapons and rocket-propelled grenades in video broadcast by Pakistani news stations. A spokesman, Muslim Khan, told reporters they were leaving Buner "of their own accord, not under any pressure," though they believe they are entitled to the territory under a peace deal with the government.

But many others remained, holing up in the mosques and religious schools or simply retreating to mountain camps, said a senior military officer. That could set the stage for a military showdown that might shatter the controversial peace deal, which handed the Swat Valley district north of Buner to the Taliban and allowed them to impose Islamic law.

The military's posture Friday was a sharp break from its silence after the Taliban overran Buner earlier this week. That had stoked U.S. and European doubts about the armed forces' commitment to battling the militants, who have deep ties to al Qaeda and the Taliban insurgents battling the U.S. in Afghanistan.

Gen. Ashfaq Kayani, army chief of staff, met with top commanders and said in a statement Friday that the military "will not allow the militants to dictate terms to the government or impose their way of life on the civil society of Pakistan."

Thousands of soldiers stationed in Swat have been put on high alert, according to the senior military officer, who added the militants there this week abducted four army officers in a "blatant violation of the peace accord."

A Pakistan security official conceded that there had been "a lot" of pressure from Washington and that Gen. Kayani had extensive discussions about the situation with Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, who visited Pakistan on Wednesday and Thursday.

But "we're not acting because they told us to do something," the official said. "We have the capability and the will to fight our own battles."

U.S. officials continued to be alarmed by Islamabad's hesitancy to fend off the offensive. Adm. Mullen told NBC News after the visit -- but before news of any Taliban pullout -- that the country was "certainly moving closer to the tipping point" of the government being overrun by Islamists. "Events continue to move in the wrong direction," he said.

Even after some Taliban retreated, there was confusion over the significance. "We're still trying to sort exactly what's happened -- or what is happening -- up in Buner," said a Western diplomat. "I don't think this is over. These guys aren't going to disappear. ... I'm afraid Pakistan doesn't recognize the threat."

The militants fought the military to a standstill in Swat, pushing the government to make the controversial peace deal. That deal didn't dull the militants' expansion aims; they set up checkpoints, took over government buildings and shut down courts in the Buner district, just 70 miles from Islamabad, the capital.

The government and military are struggling to find a cohesive strategy to halt the militants' advance and reassert authority, say Pakistan officials and foreign diplomats. Testifying on Capitol Hill, Gen. David Petraeus, commander of U.S. forces in the Middle East and Central Asia, said that while the Pakistani army has taken serious losses in combating extremists, the rest of the Pakistani government appeared less committed to the fight. The U.S. seeks a "complete commitment by the Pakistani senior leaders" to allow its military to clamp down on the threat, he said.

The Pakistani security official said there is a growing sense in the military ranks that they would sooner or later have to renew their fight against the Taliban. Some recent statements from Taliban leaders in Swat -- they've denounced democracy, called Pakistan's courts un-Islamic and said they would welcome Osama bin Laden to the valley -- also have helped to focus the country's top brass on the threat. "We have very different ideas of what a peace deal is," said the security official.

The military agreed to the peace deal, Gen. Kayani said Friday, "to give the reconciliatory forces a chance" and not as a concession to the militants. But persistent doubts remain about the military's priorities. Nearly 80% of its forces are dug in on the eastern border with India.

That's left the forces battling the Taliban thinly stretched, and often resulted in the military cutting its own deals with Taliban factions. A U.S. official, speaking from Washington, said that as late as Thursday, the military was refusing to move soldiers from the Indian border to Buner.

The peace deal -- which Pakistan says didn't include Buner -- was negotiated by a radical cleric, Sufi Mohammed, who also helped convince some of the Taliban to leave Buner Friday, said Syed Mohammed Javed, the top government official in the region.