Pakistan's government has begun rallying support both at home and abroad as tension flared with old rival India after a bloody militant assault on the Indian city of Mumbai.
India said on Sunday it had proof of a Pakistani link to the Mumbai attacks that killed nearly 200 people, raising the prospect not only of a breakdown of peace efforts between the nuclear-armed nations but of confrontation across their border.
Pakistan condemned the assault as a "barbaric act of terrorism" and denied any involvement by state agencies.
It has vowed to cooperate in fighting terrorism but backtracked on a decision to send the chief of its spy agency to India to help with the investigation, in a move likely to revive questions about who is in charge of the shadowy organisation.
Pakistan has also said it would move troops from its western border with Afghanistan, where security forces are battling al Qaeda and Taliban fighters as part of the U.S.-led campaign against militancy, to the Indian border if tension escalated.
Prime Minister Yousaf Raza Gilani telephoned opposition politicians late on Saturday to brief them on the crisis.
"These political leaders assured the prime minister of their full support and cooperation at this critical juncture," Gilani's office said. Gilani had cancelled a trip to Hong Kong, an official said.
Foreign Minister Shah Mehmood Qureshi spoke by telephone to the foreign ministers of China and the United Arab Emirates as well as European Union foreign policy chief Javier Solana, and told them Pakistan had promised all help to India.
"Terrorism is a menace to humanity and it must be eliminated," the Foreign Ministry said.
India and Pakistan have fought three wars since gaining independence in 1947 and went to the brink of a fourth after a 2001 militant attack on the Indian parliament that New Delhi also blamed on Pakistan.
Both sides massed hundreds of thousands of troops on the border and fought daily artillery duels across their frontier in the disputed Kashmir region.
The United States, alarmed war between its allies would derail efforts against al Qaeda and the Taliban in Afghanistan, helped cool tempers. The two sides declared a ceasefire in Kashmir in late 2003 and soon embarked on a peace process.
U.S. President George W. Bush said on Saturday he had been closely monitoring the Mumbai attacks.
The attacks came after Pakistani President Asif Ali Zardari, widower of former prime minister Benazir Bhutto who was assassinated last year, had made bold moves to improve ties with India.
Zardari, battling Islamic radicals at home, told Indian television on Saturday he would cooperate in the investigation and act decisively if any Pakistani link was found.
"If any evidence comes of any individual or group in any part of my country, I shall take the swiftest of action in the light of evidence and in front of the world," he told CNN-IBN.
Pakistan says India is too hasty to blame it for attacks when New Delhi has homegrown militants. But Pakistan has a history of using militants to further foreign policy objectives, initially to battle Soviet forces occupying Afghanistan in the 1980s. Pakistan supported militants fighting Indian forces in the disputed Kashmir region for years but began to rein them
in after the Sept. 11 attacks on the United States.
The Mumbai assault bore the hallmarks of Pakistan-based militant groups such as Lashkar-e-Taiba or Jaish-e-Mohammed, blamed for the 2001 attack on the Indian parliament.
Lashkar-e-Taiba and a Kashmiri militant leader denied any role. Instead, the little-known Deccan Mujahideen claimed responsibility.
A senior Pakistani security official denied the involvement of any Pakistani institution in the Mumbai attack and said the war on terror would not be a priority if tension escalated.
The next day or two would be crucial in assessing India's response, the official, who declined to identified, told a small group of reporters on Saturday.