The US military's top officer accused Pakistan on Thursday of "exporting" violent extremism to Afghanistan by allowing militants to act as an "arm" of Islamabad's intelligence service.
In an unprecedented public condemnation of Pakistan, Admiral Mike Mullen said the country's Inter-Services Intelligence (ISI) was actively supporting Haqqani network extremists who he said have targeted US forces in Afghanistan.
"In choosing to use violent extremism as an instrument of policy, the government of Pakistan -- and most especially the Pakistani Army and ISI (intelligence service) -- jeopardizes not only the prospect of our strategic partnership, but also Pakistan's opportunity to be a respected nation with legitimate regional influence," Admiral Mike Mullen told US senators.
"By exporting violence, they have eroded their internal security and their position in the region. They have undermined their international credibility and threatened their economic well-being," Mullen said.
His comments follow a series of tough warnings from top US officials on Pakistan's approach to Islamist militants, suggesting possible unilateral US action.
"The Haqqani network... acts as a veritable arm of Pakistan's Inter-Services Intelligence Agency," Adm Mike Mullen told a Senate panel.
Some 25 people died in last Tuesday's 20-hour attack on Kabul's US embassy and other official buildings. The dead included 11 civilians, among them children, along with at least four police and 10 insurgents.
"With ISI support, Haqqani operatives planned and conducted a truck bomb attack, as well as the assault on our embassy," said Adm Mullen, who steps down this month as chairman of the US Joint Chiefs of Staff.
"We also have credible intelligence that they were behind the 28 June attack against the Inter-Continental Hotel in Kabul and a host of other smaller but effective operations."
The Haqqani network, which is closely allied to the Taliban and reportedly based in Pakistan, has been blamed for several high-profile attacks against Western, Indian and government targets in Afghanistan.
(with inputs from BBC)