With the number of attacks in eastern Afghanistan up by 40 percent from a year ago, senior Bush administration officials have been voicing increasing alarm about the growing strength of the militants using havens in Pakistan.

“The ability of the Taliban and other insurgents to cross that border and not being under any pressure from the Pakistani side of the border is clearly a concern,” Defense Secretary Robert M. Gates told reporters two weeks ago in one of his most pointed comments to date on the situation. “That’s the area that needs to be addressed with the Pakistani government.”

The Bush administration is struggling to work with the Afghan and Pakistani governments to find an effective combination of political, diplomatic and military tools to help stem the increasingly entrenched insurgency, but it has faced difficulties dealing with Pakistan’s new coalition government, officials say.

“We’re trying to impress upon the Pakistanis how bad things are,” said one senior administration official, who spoke on condition of anonymity because of diplomatic sensitivities. “Before, we could go to Musharraf,” the official said, speaking of President Pervez Musharraf. “Now it’s more of a power-sharing agreement, and it’s more difficult. There’s no apparent solution at hand. The next six months look like they’ll be a lot like the past six months.”

Four senior military officials said that Al Qaeda was strengthening its increasingly close operational ties in the tribal areas with the Taliban and various other militant groups  financing, training recruits and facilitating attacks into Afghanistan, though not necessarily conducting attacks themselves.

Inside Pakistan, the forces of the Tehrik-e-Taliban of Pakistan, an umbrella group of Taliban, are most prominent among the militants. The group is led by Baitullah Mehsud, who is accused by the Pakistani government of masterminding the assassination of former Prime Minister Benazir Bhutto in December and running scores of suicide bombers on both sides of the border.

Mr. Mehsud, who has risen from near obscurity to become a powerful ally of Al Qaeda, brazenly held a news conference in May in his home base, South Waziristan, to announce that he would expand his fight against the American military across the border in Afghanistan, where the group has close links to other Taliban forces.