The United States has pressed Pakistan to confront Taliban militants whose influence is spreading in the nuclear-armed country but said it supports Pakistani President Asif Ali Zardari.
"Pakistan must demonstrate its commitment to rooting out al-Qaeda and the violent extremists within its borders," Richard Holbrooke, the US special representative for Afghanistan and Pakistan, said in prepared congressional testimony.
Despite the criticism, Mr Holbrooke sent an clear signal of support for Zardari, widower of former Pakistani Prime Minister Benazir Bhutto, who was assassinated in 2007.
"We have the highest strategic interests in supporting this government," Mr Holbrooke said. "Our goal must be unambiguously to support and help stabilise a democratic Pakistan headed by its elected president, Asif Ali Zardari."
Mr Holbrooke, who brokered the 1995 peace agreement that ended the Bosnian war, dismissed the idea that Pakistan is disintegrating and said it was not a "failed state."
However, US lawmakers voiced deep concern about Pakistan during the hearing, sometimes in blunt terms.
"Pakistan's pants are on fire." said Representative Gary Ackerman, a Democrat who launched a scathing criticism of Mr Zardari.
"Zardari has said the right things . . . but in practice his government's response has been slow, weak and ineffective. The fire is real and they need to respond."
President Barack Obama meets the Afghan and Pakistani presidents in Washington today for talks expected to focus on fighting the Taliban's insurgency in Afghanistan as well as its growing influence in neighbouring Pakistan.
The three-way talks aim to promote co-operation between Afghanistan and Pakistan, which Taliban militants use as a base to attack Afghan targets, but have been overshadowed by US concerns about Pakistan's stability.
US officials are worried about the strength of Pakistan's Taliban militants, who have advanced beyond a stronghold in the Swat valley, to Buner valley, 60 miles northwest of the capital, Islamabad.
Pakistani security forces launched an offensive to expel militants from Buner and another district on April 26th. About 180 militants have been killed, according to the military, although there has been no independent confirmation.
Hundreds of people fled the Swat valley's main town yesterday after a Pakistani official warned of possible fresh fighting between government forces and the militants.
The Pakistani government offensive follows criticism by American officials, lawmakers and analysts who accuse Mr Zardari of having done too little to undercut the Taliban.
Sixty-four militants were killed today in fighting in northwest Pakistan, security forces said.
The army said 37 militants were killed in two clashes in the Swat Valley, where a peace deal aimed at ending Taliban violence has collapsed. Two soldiers were also killed.
A paramilitary force said 27 militants were killed in the nearby Buner district.
Reuters