WASHINGTON, Sept 23: Simmering tensions between the United States and Pakistan reached a boiling point on Friday as the White House urged Islamabad to cut its ties to the Haqqani network while Pakistani leaders rejected the US claim as unfortunate and incorrect.

“It is critical that the government of Pakistan break any links they have and take strong and immediate action against this network,” White House spokesman Jay Carney told a briefing in Washington. “So that they are no longer a threat to the United States or to the people of Pakistan, because this network is a threat to both.”

The White House backed the allegation that Admiral Mike Mullen, the US Joint Chief of Staff Chairman, had made in the Senate on Thursday, claiming that Haqqani operatives launched an attack last week on the US embassy in Kabul with ISI’s support.

Pakistan’s strong reaction to the US allegations figured at the White House briefing on Friday where a reporter asked: “Any reaction from the White House to the remarks from Pakistan that the alliance is threatened by the sort of claims by Admiral Mullen in front of the Senate?”

“We believe — we know that the Haqqani network was responsible for the attacks on the Kabul embassy, our embassy in Kabul, the Isaf headquarters and a number of other recent attacks that caused death and injury not only to Afghans but to US soldiers,” the White House spokesman responded.

“And we know that the Haqqani network operates from safe havens in Pakistan and that the government of Pakistan has not taken action against these safe havens.”

Pakistan’s failure to act against the Haqqani network had been “a long-standing concern of the United States and one that we’ve discussed with Pakistan in public and in private”, said Mr Caney.

“Senior officials, including Chairman Mullen and Secretary Clinton, met with their Pakistani counterparts to make this point earlier in the past week or so, and we will continue these discussions and seek action on the part of Pakistan.”

“Does President Obama believe that Pakistan is a reliable partner?” asked another journalist.

“Look, we have an important relationship with Pakistan. That relationship and the cooperation that we have had with Pakistan has assisted us greatly in our efforts to defeat Al Qaeda. And it is important to remember that Pakistan has suffered mightily at the hands of terrorists, and they paid a terrible price for it,” said the White House official. “It is a complicated relationship, as you’ve heard me say before. And when we have issues that we need to discuss with the Pakistanis, we’re very candid and forthright in doing so … And those continue — those conversations will continue.”

Other US officials who spoke to the media claimed that growing US frustration over Pakistan’s alleged collusion with Afghan militants had forced them to go public with their accusations.

The commander of US and Nato forces in Afghanistan, US Marine Corps Gen John Allen, also turned up the heat when he revealed that he had personally given the Pakistani army chief intelligence information about a possible terror attack and Gen Kayani said he would “make a phone call” to stop it but did not.

The attack was the truck bombing two days later, said reports in the US British media which attributed the information to Gen Allen.

Meanwhile, top US lawmakers are pressing Secretary of State Hillary Clinton to put the militant Haqqani network on the terror blacklist immediately, citing testimonies by officials that the outfit was an “arm” of the Pakistan’s military intelligence.

“I request that the State Department list the network as a foreign terrorism organisation,” said Senate Intelligence Committee Chairwoman Dianne Feinstein.

She said in a statement that the Haqqani network “met all the standards of the blacklist as it has been conducting attacks against US targets and personnel in Afghanistan and poses a continuing threat to American, Afghan and allied personnel and interests”.

Another leading senator, Carl Levin, Chairman of the Senate Armed Services Committee, asked at a Congressional hearing why was there an inordinate delay in designating the network as a terrorist organisation.

“This step is long overdue,” Mr Levin said. “I hope the State Department will move quickly to designate the Haqqanis as a foreign terrorist organisation,” Senator Levin said as he and other lawmakers had urged Defence Secretary Leon Panetta and Admiral Mullen to take steps to ensure that the Haqqani network was not able to attack Americans.