AN AFGHAN warlord was last night preparing to attack a suspected mountain hideout where he thinks Osama bin Laden is in hiding with 600 Taliban and al-Qaida fighters.

Hazrat Ali, the security chief for eastern Nangarhar province, said a final decision to launch the attack on Tora Bora had not been taken. The camp is in a high mountain valley filled with caves near the Pakistani border.

But Ali said anti-Taliban forces must act soon if the non-Afghan fighters fail to surrender.

Tora Bora is a well-known cave complex built in the 1980s with US funding as a headquarters for guerrillas fighting against the Soviet occupation.

Ali, who fought the Soviets from Tora Bora, has described it as an impregnable fortress. He advised US forces from attacking it alone.

Meanwhile, the US warned there must be no amnesty for the beleaguered Taliban leader, Mullah Mohammed Omar.

Opposition fighters were reported to be closing in round the southern Afghan city of Kandahar, the former regime's last stronghold, where Mullah Omar has ordered his supporters to fight to the death. The Pentagon said the situation in the area remained "fluid", with negotiations taking place between the opposition forces and the Taliban for the city's surrender.

However, US Defence Secretary Donald Rumsfeld made clear that America would fiercely resist any deal that allowed Mullah Omar - who is thought to be in the area - to go free.

He said: "I can assure you that the United States would vigorously oppose any idea of providing him amnesty or safe passage of any type."

The talks in Bonn on Afghanistan's future were in disarray at a critical phase last night, with the Northern Alliance refusing to present a list of names to help rule the country until a national council next spring.

Alliance chief envoy Younus Qanooni told the other delegations he was not in a position to agree to any names.