Updated

The top U.S. military officer said Friday that he thinks it is possible that the Pakistani military can shut down Taliban hideouts on its soil to prevent insurgents from moving back and forth across the long, porous border with Afghanistan.

A day after President Barack Obama released a review of the U.S. war strategy, Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, told reporters in Kabul that fixing the problem is critical to making progress in the war. But he said he's encouraged by what Pakistan has already done to go after insurgents on its side of the border.

"I certainly think it is very possible that the Pakistani military will achieve the goal," he said.

A five-page public summary of the White House's classified Afghanistan War review said dealing with safe havens would require greater cooperation with Pakistan along the border. The areas of most concern — the Pakistani provinces of North Waziristan and Baluchistan — are not mentioned by name.

Pakistan has made progress against safe havens over the past year in operations that have taken a toll on its forces, the summary said. But Pakistani authorities have almost exclusively focused on militants who pose a threat inside Pakistan. So far they have refused a U.S. request to take on militants in North Waziristan, the place used most frequently to target U.S. forces.

Mullen spoke to reporters in the Afghan capital alongside Karl Eikenberry, the U.S. ambassador to Afghanistan, who said the existence of insurgent sanctuaries in Pakistan "makes delivery of peace and stability here in Afghanistan very difficult."

Gen. David Petraeus, the top commander of U.S. and NATO forces, praised Pakistan's efforts to rout militants inside the country, and its new willingness to cooperate with NATO forces on the Afghan side of the border.

Petraeus gave two recent examples of joint operations spanning the eastern border with Pakistan, in which NATO and Pakistan forces ran a lethal squeeze play on militants. In one case, NATO forces drove militants toward Pakistan, and in the other Pakistani forces flushed militants toward NATO forces.

Pakistani leaders understand the threat of militants of all stripes, Petraeus said, a reference to the historical practice of tolerating or supporting some extremist groups as a political pressure valve and a hedge in the rivalry with India.

"I think that there is growing recognition ... that extremists of any type on Pakistani soil inevitably are a source of problems," Petraeus said.

Full recognition of that, and a national decision to expunge the worst problems, would mean targeting the powerful Haqqani network of extremists, which operates on both sides of the border.

The group is blamed for many of the deadliest attacks on U.S. troops in Afghanistan. Analysts and Afghan government officials have accused Pakistan of protecting the Haqqani network as allies who could be of use after the Americans and their allies leave Afghanistan.

U.S. and NATO officials have begun talking about the sanctuary problem in more nuanced terms over the past year, backing away from stark demands that Pakistan wipe out the havens and praising Pakistan for attacking homegrown militants on a large scale.

U.S. military officials are pushing back against the recent assertion by U.S. intelligence officials that the Afghanistan War cannot be won unless Pakistan eliminates the sanctuaries, and that Pakistan has decided not to do so. Improving trends in other areas may make the sanctuary problem less acute over time, Maj. Gen. John Campbell told reporters this week. He commands NATO coalition forces in eastern Afghanistan, across the border from North Waziristan and the Haqqani home base.

Two American missile attacks killed 15 people Friday in a region in northwest Pakistan that has seen few such strikes in the past, Pakistani officials said, possibly signaling an expansion of the CIA-led covert war inside the country. The same valley, known to be home to Islamist militants, was hit late Thursday in another U.S. attack. The officials spoke on condition of anonymity because they were not authorized to talk to the media.

Also Friday, the CIA pulled its top spy out of Pakistan after threats were made against his life, current and former U.S. officials said. A Pakistani lawsuit had accused the CIA station chief by name of killing civilians in drone strikes, leading to threats on his life. The Associated Press is not publishing the station chief's name because he remains undercover and his name is classified.

The Taliban on Friday rejected the review of Obama's year-old war strategy in Afghanistan, saying that it has failed on both the military and the civil administration fronts.

In an e-mailed statement, Taliban spokesman Zabiullah Mujahid said the last nine years of war had proven that increased troop levels had no effect. "Corruption, insecurity and the civilian casualties are a result of failed American strategy," Mujahid said.