Another central concern is the war in Afghanistan, which has been fueled by Taliban and Qaeda fighters who have used Pakistan as a rear base to carry out increasingly lethal and sophisticated attacks across the border.

After years in which Mr. Musharraf proved unable or unwilling to rein in militants in Pakistan, American officials say they are now more skeptical than ever that they can count on cooperation from Pakistan’s military leaders, even including Gen. Ashfaq Parvez Kayani, a former head of Pakistan’s spy agency, who replaced Mr. Musharraf as military chief last November.

The coalition government had “no comprehension” of the insurgency, said a former interior minister, Aftab Ahmed Khan Sherpao, whose parliamentary constituency adjoins the tribal areas. “They have one policy for domestic consumption: ‘Have peace, don’t use the army,’ ” he said. “Then for the foreigners they say, ‘We will fight.’ ”

Image A picture released by the Pakistani government of President Pervez Musharraf announcing his resignation to the nation in a televised address. Credit... Press Information Department/Agence France-Presse — Getty Images

A main challenge for Washington now will be to fix the attention of the two leaders of the coalition parties, Asif Ali Zardari and Nawaz Sharif, on the raging Taliban insurgency that not only threatens American soldiers in Afghanistan but also threatens to destabilize Pakistan itself.

The campaign against the militants is unpopular here in Pakistan because it is seen as an American conflict foisted on the country. Washington would like the new government to explain to the public that the effort to quell the Taliban is in Pakistan’s interests as well.

So far, the coalition, distracted by internal machinations, has failed to make that case, even as the military has taken on the insurgents with new vigor in the last 10 days. Secretary of State Condoleezza Rice sought on Monday to emphasize continuity with the new leaders of Pakistan, saying the United States would keep pressing the Pakistani government to battle extremism within its borders.