The Pakistan Taliban has blamed the Nawaz Sharif government for the death of their chief Hakmullah Mehsud and said it would not hold any peace talks with the "puppet government", prompting the prime minister to chair a meeting of his top security advisors on Monday evening to review relations with the US.
The killing of the chief of the Tehreek-e-Taliban Pakistan (TTP), as the militant group Mehsud headed was formally called, in a drone attack on Friday by the US has sparked a furious response from Islamabad.
The government was taking the first steps towards initiating talks with the militants when Mehsud was killed, leading interior minister Chaudhry Nisar to accuse Washington of "scuttling" peace efforts.
Afghan President Hamid Karzai, too, added his voice to criticism of the US, saying the killing of Mehsud came at "an unsuitable time" and hoping the peace process did not suffer as a result.
As a reaction to drone attack, the Tehreek-e-Taliban Pakistan spokesman Shahidullah Shahid was quoted by the Geo News as saying: "After consultation with all the factions it has been unanimously decided that we will not hold any peace talks with the government. It's a puppet government of the US and it deceived us in the name of peace talks."
The spokesman said the killing of Mehsud had proved that the government was not serious about holding peace talks.
"We did not want innocent Pakistani people to suffer any more and therefore decided to hold negotiations with the government. But the government, by helping the US in the killing of Hakimullah Mehsud, proved that there was zero sincerity in the mind of the rulers. It was neither sincere nor serious in peace negotiations," he said.
Nawaz Sharif came to power in May partly on a pledge to hold talks to try to end the TTP's bloody insurgency that has fuelled instability in the nuclear-armed nation.
On Saturday, a furious Nisar said "every aspect" of Islamabad's ties with Washington would be reviewed by the cabinet security council, at a time when they appeared to be warming after lurching from crisis to crisis in 2011 and 2012.
Opposition parties led by Imran Khan's Pakistan Tehreek-e-Insaaf (PTI) party have demanded the government close Pakistan's roads to convoys supplying NATO forces in Afghanistan.
Pakistan Tehreek-e-Insaaf has said it will block NATO convoys in the northwestern province of Khyber Pakhtunkhwa where it is in power, which would cut off one of the main crossing points into Afghanistan.
Pakistan blocked NATO convoys for seven months in 2012 after a botched US air raid killed 24 troops.
With NATO withdrawing 87,000 troops from Afghanistan by the end of next year after 12 years of war, the ground supply lines through Pakistan are of vital importance.
Anti-American sentiment runs deep in Pakistan and drone strikes are hugely unpopular, with many criticising them both for civilian deaths and as a violation of sovereignty.
But after the heated rhetoric of the weekend, Sharif and his government must weigh the practicalities of their response carefully in the light of improving relations with a vital financial partner.
Last month US President Barack Obama welcomed Sharif to the White House and the State Department announced the release of $1.6 billion in aid, including $1.38 billion for the country's powerful military.
The money had been frozen as relations plummeted amid a series of crises in 2011 and 2012, including the US raid to kill Osama bin Laden at his hideout in Pakistan -- carried out without Pakistani knowledge.
Washington has said the issue of whether to negotiate with the TTP was an internal matter for Pakistan, but stressed the US and Pakistan had "a vital, shared strategic interest in ending extremist violence".