In a frank debate on Friday with the White House war adviser Douglas Lute, she said the drone attacks succeeded in damaging al-Qaeda but were now only serving to recruit new militants.

The two were speaking to an audience at the Aspen Security Forum.“I am not saying drones have not assisted in the war against terror, but they are diminishing rate of returns now,” the envoy said, speaking by video teleconference from Washington.

“We will seek an end to drone strikes and there will be no compromise on that,” she added.Lute would not comment on the drone strikes, but US officials have said privately that the strikes will continue because Pakistan has proved incapable or unwilling to target militants the US considers as dangerous.

Sherry defended arrest of Dr Shakil Afridi, who has been sentenced to more than three decades in prison for aiding the CIA in tracking down Osama bin Laden.

The US lawmakers have threatened to halt millions of dollars in aid to Pakistan if Afridi was not released.“He had no clue he was looking for Osama,” Sherry countered. “He was contracting with a foreign intelligence agency.”

She added that Afridi’s actions put thousands of children at risk because some vaccine programmes had to be ended after Pakistani aid workers were targeted by the Taliban.

She also dismissed as “outrageous” a claim by some US lawmakers that Pakistan is harbouring al-Qaeda or other militants who intend to harm their country.

The envoy said Pakistan’s army was working hard to combat the militants, including reporting 52 times to the Nato in recent months when militants were spotted crossing into Afghan territory.

“Pakistan is maxed out on the international border with Afghanistan” she said of Pakistani efforts.“Sovereignty has privileges but also comes with responsibilities,” countered Lute who called for Pakistan to step up its efforts and to cease “hedging its bets” by supporting the Afghan Taliban.

The two did agree, however, that Pakistan could help broker an eventual peace deal with the Taliban.