The U.S. troop surge in Afghanistan is unlikely to work unless the Taliban and its allies are denied the sanctuary they enjoy across the border in Pakistan. That's why two top U.S. military commanders, General David Petraeus, the head of U.S. Central Command, and Admiral Mike Mullen, the Chairman of the Joint Chiefs of Staff, visited Islamabad this week to press their Pakistani counterparts for action on Afghan Taliban networks based in Pakistani North Waziristan and around the city of Quetta. But even as the Pakistani military fights a full-scale counterinsurgency war against the Tehrik i-Taliban Pakistan (TTP, also known as the Pakistani Taliban), it remains reluctant to extend its targets to include the groups that most concern the U.S. (Read "Pakistan: Behind the Waziristan Offensive.")

The argument most often used by Pakistani officials to rebuff Washington's demands for action against the Afghan-Taliban allied Haqqani network and Gulbuddin Hekmatyar's Hizb-e-Islami, as well as the Afghan Taliban leadership core in Quetta, is about resources and priorities. Pakistan has committed 30,000 troops to its offensive against the TTP in Swat and South Waziristan, they argue, and it simply doesn't have the resources to open a second front against the Haqqani network in North Waziristan (which is also where al-Qaeda's leaders are believed to be hiding). General Ashfaq Kiyani reportedly told Petraeus that Pakistan's priority, given its limited resources, was on the TTP insurgency, which directly challenges the Pakistani state. (See pictures of the battle against the Taliban.)

"Don't overstretch us," says Talat Masood, a retired lieutenant general turned analyst, explaining the army's reaction Washington's plans for Afghanistan. "If that happens then even the current operation [against the Afghan Taliban] will be directly affected. Please understand our predicament. You don't want our current operations to fail."

Pakistani officials advancing this argument often imply that once the domestic insurgency has been suppressed, the Army can move on to tackling the groups that most concern the U.S. But many analysts believe that Pakistan's reluctance to go after Haqqani, Hekmatyar and the Afghan Taliban leadership in Quetta is based not only on resources and priorities, but on the Pakistani military's assessment of its long-term interests in Afghanistan after the U.S. leaves. (See pictures of an attack on a Pakistani police academy.)

The fearsome North Waziristan-based network led by ailing former Afghan mujahedeen commander Jalaluddin Haqqani and run by his son, Sirajuddin, controls three key Afghan provinces that border Pakistan - Khost, Paktia, and Paktika provinces. The network has a longstanding relationship with Pakistan's Inter Services Intelligence organization, and is viewed by many in the Pakistani military as an important strategic asset in the regional struggle for influence in Afghanistan. (Some reports suggest that this has become a matter of some debate within the Pakistani military.) Those who share this view believe that the group can be separated from al-Qaeda and could form part of a compromise political solution in Afghanistan which Pakistan hopes to play a key role in brokering. A similar logic is likely to be at work with respect to Hekmatyar, and even the Afghan Taliban leadership. It's a view based on seeing the Afghan Taliban as a Pashtun nationalist movement challenging the new Tajik-dominated political order in Kabul - which is also deemed by many in Pakistan to be a proxy for India. There's also concern that mounting an offensive against Taliban groups that confine their attacks to Afghanistan will rouse Pashtun fury on both sides of the border, imperiling Pakistan's domestic counterinsurgency effort.

A version of that thinking in Pakistani circles was expressed this week by Munir Akram, Pakistan's former Ambassador to the U.N., writing in The News: "To eliminate al-Qaeda in the Afghanistan-Pakistan border region, it must be separated and isolated from the Taliban 'sea' in which it is currently hiding," argued Akram. "But the U.S. troop surge will be mainly directed against the Taliban insurgency. It will push al-Qaeda and the insurgents closer together, making it more difficult to isolate and target al-Qaeda." He also argued that going after the Afghan Taliban, which is seen as America's enemy rather than Pakistan's, will weaken Pakistan's national consensus supporting the offensive against the TTP.

The immediate focus of discussion between the U.S. and Pakistan is North Waziristan. While the Pakistan army has cleared swaths of territory once controlled by the TTP in South Waziristan and claims to have killed over 600 militants, it has not managed to kill or capture any of the leadership, who have largely fled north along with many fighters. That certainly gives Pakistan's army a pretext for pushing into North Waziristan - as the U.S. is urging - although any such operation would likely be a limited one, focused on TTP groups and concentrated in areas where they would avoid clashing with the Haqqani fighters.

If the Pakistani military declines to go after the Afghan Taliban, the U.S. faces limited options for turning up the heat. Unable, politically, to commit ground forces to Pakistani territory, it would be forced to rely on the remote-controlled drone strikes that have been effective in killing al-Qaeda leaders in the area. Conflicting reports in the U.S. media suggest that either President Obama plans to expand those operations precisely to target the Afghan insurgent groupings that remain largely unmolested in Pakistan, or that he's reluctant to authorize strikes that go beyond the targets agreed by Pakistan, for fear of jeopardizing cooperation and triggering a political crisis. But if the goal is to reverse the Taliban's momentum in Afghanistan, the U.S. may feel it has no choice. And that's certainly the message it wants Pakistan - and the Taliban - to take from the current conversation.