ISLAMABAD (AP) -- U.S. pressure on Pakistan to attack Afghan militants on its soil will not succeed, the Pakistani prime minister told a gathering Thursday of political and military leaders trying to formulate a response to fresh American allegations that the army’s spy agency is supporting the insurgents.

The claims last week by Adm. Mike Mullen, America’s top military officer, sent relations between Islamabad and Washington plummeting and triggered a nationalist, anti-American backlash across Pakistan.

Much of the focus has been on veiled U.S. threats of unilateral action against Afghan militants sheltering on the Pakistan side of the border.

“Pakistan cannot be pressured to do more, but the doors are still open from our side for talks and discussion,” said Prime Minister Yousuf Reza Gilani. “We reject these allegations. God willing, we can face these challenges with unity. We are committed to defend our independence and sovereignty.”

Intelligence chief Lt. Gen. Ahmed Shuja Pasha was also scheduled to address the gathering, which was closed to the media, apart from Gilani’s opening remarks.

U.S. officials have long talked with Islamabad about links between Pakistan and the militant Haqqani network that is behind much of the violence in Afghanistan. But those discussions were mostly held in private, in the hope that Pakistan could gradually be persuaded to sever the purported ties with the group.

But Mullen seemed to signal a new approach last Friday when he told Congress that that Haqqani network was a “veritable arm” of the spy agency, which he said supported the militants in a recent attack on the U.S. Embassy in Kabul.

Pakistani officials have denied the allegations, and accused Washington of making them a scapegoat for U.S. failures in Afghanistan.

Most of Pakistan’s feuding political party leaders were present at Thursday’s meeting, a sign of how U.S. threats can unite them. The attendants are expected to issue a resolution condemning the United States but it’s unclear whether the statement will touch on the allegations of Pakistan support for Afghan militants, a far more sensitive topic because it could set off criticism of the powerful army.

The army, not the elected government, controls Afghan policy and will ultimately decide the future course of action on the issue.

Most analysts say the Pakistani army and the spy agency are tolerating or even supporting the Haqqani network because they want to cultivate it as an ally in Afghanistan once the Americans withdraw. They see little chance of the top brass attacking the group now, especially when the U.S. is calling for peace talks with other militant factions in Afghanistan.

This view has support in Pakistan, where many people perceive the Americans as the illegitimate force in Afghanistan, not the Afghan Taliban. But others oppose it because the militants are ideologically allied to al-Qaida and other extremists who have carried out scores of bombings on Pakistani soil over the last four years.

Meanwhile, an explosion ripped through the fourth floor of a small hotel in Islamabad late Thursday, injuring four people, smashing windows and throwing chunks of concrete onto cars in the parking lot in front of the building.

Islamabad police chief Mohammed Binyamin told reporters at the scene that the blast was caused by a gas leak, not by a bomb. The explosion took place at the City Hotel, a small establishment popular with local businessman and travelers in the heart of the capital.