The United States has long demanded Pakistan go after the Haqqani network in North Waziristan that has staged attacks on NATO-led forces in Afghanistan.
But top officers indicated they did not expect any improvement in Islamabad's cooperation and that Pakistan lacked the will and the resources to move against Haqqani militants.
"Sir, I don't think it is likely to change," Vice Admiral William McRaven, who oversaw a raid last month by Navy SEALs that killed Osama bin Laden in his Pakistani hideout, told senators.
Referring to talks with Islamabad military leaders, McRaven said "it is both a capacity issue for the Pakistanis and I think potentially a willingness issue."
McRaven, nominated by President Barack Obama to take over US special operations command, said the situation in northwest tribal areas "is difficult for them to deal with."
Lieutenant General John Allen, named as the next commander in Afghanistan, suggested Pakistan was keeping its options open by allowing Haqqani fighters to operate within its borders.
"It's a function probably of capacity. But it might also be a function of their hedging, whether they have determined that the United States is going to remain in Afghanistan, whether our strategy will be successful or not," Allen told the Senate Armed Services Committee.
"At some point, as we have emphasized to the Pakistanis, we've got to bring pressure to bear on this insurgent safe haven," he said.
Senator Carl Levin, after hearing the officers answer his questions on Pakistan, said Islamabad's approach was unacceptable.
"Well, something's got to give, something's got to change," Levin said.
His comments came amid calls from some lawmakers to scale back the billions in US aid for Pakistan due to the presence of extremist safe havens.
Another senator, Lindsey Graham, said it was time Pakistan track down the leader of the Afghan Taliban, Mullah Omar.
McRaven confirmed to Graham that the US military believed Omar was in Pakistan and had asked the country's army to find him.
General Allen also confirmed, when asked by Graham, that roadside bombs used to assault US-led forces were being constructed in Pakistan and that the United States had provided Islamabad with information about the location of bomb-making sites.
COMMENTS (53)
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ
Why should Pakistan attack them when (as per Sethi) US itself wants to get into talks with the network?