WASHINGTON: The United States on Tuesday renewed blunt demands that Pakistan crack down on Haqqani militants allegedly based in the country, saying the network posed a serious threat to US forces in Afghanistan.

Defence Secretary Leon Panetta told reporters that Washington would “put as much pressure as possible on the Pakistanis to exercise control from their side of the border.”

“We’ve continued to state that this cannot happen, we cannot have the Haqqanis coming across the border, attacking our forces, attacking Afghanistan...and then disappearing back into a safe haven. That is not tolerable,” Panetta said.

He added: “I think they’ve heard the message, but we’ll see.”

Panetta’s comments reflect a tougher public US line in recent days amid growing frustration in President Barack Obama’s administration over the role of the Haqqani network.

The stern warnings also coincide with increasingly strained relations with Pakistan.

The Americans blame the Haqqani network for a recent bombing attack that wounded 77 US troops at a base in Wardak province and for an elaborate assault on September 13 on the US embassy and Nato headquarters in Kabul.

Admiral Mike Mullen, chairman of the Joint Chiefs of Staff, said at an earlier event Tuesday the presence of the Haqqani sanctuaries potentially jeopardised the outcome of the war.

“Without that (Pakistani action), we can’t succeed in the overall effort,” he said.

Mullen said Pakistan’s ISI intelligence agency had to sever all ties with the Haqqani militants, who allegedly operate out of sanctuaries in the country’s northwest.

“I think that the ISI has to make the decision to strategically disengage. The ISI has been doing this, supporting proxies for an extended period of time,” he told an audience at the Carnegie Endowment for International Peace.

Mullen met with his Pakistani counterpart over the weekend in Spain, General Ashfaq Kayani, and repeated Washington’s impatience on the Haqqani militants.

At the Pentagon press conference, Mullen — who has held numerous talks with Kayani during his four year tenure — said there was no doubt about “the clarity with which I addressed this issue” in the meeting with the Pakistani general.