For the first time, the Taliban offered to hand over Bin Laden for trial in a country other than the US without asking to see evidence first in return for a halt to the bombing, a source close to Pakistan's military leadership said.

But US officials appear to have dismissed the proposal and are instead hoping to engineer a split within the Taliban leadership.

The offer was brought by Mullah Wakil Ahmed Muttawakil, the Taliban foreign minister and a man who is often regarded as a more moderate figure in the regime.

He met officials from the CIA and Pakistan's ISI intelligence directorate in Islamabad on Monday. US officials pressed the minister for a sweeping change in the regime. "They are trying to persuade him to get the moderate elements together," another source said.

Mr Muttawakil's visit coincided with the arrival in Islamabad of Colin Powell, the US secretary of state. After several hours of talks with Pakistan's military ruler General Pervez Musharraf yesterday, Mr Powell admitted that moderate Taliban would play a role in talks on a future Afghan government. "We would have to listen to them or at least take them into account," he said.

Mr Powell also met envoys sent by Zahir Shah, the former Afghan king who lives in exile in Rome, and a representative of the opposition Northern Alliance, sources said.

The Taliban foreign minister had asked for face-to-face talks with the US secretary of state but no direct meeting was held. Mr Muttawakil returned to Kabul last night and the Taliban have publicly denied he was ever in Islamabad.

His visit came as Taliban forces in Afghanistan came under renewed pressure from the bombing campaign and opposition advances.

Troops from the Northern Alliance were yesterday closing in on the key northern town of Mazar-i-Sharif. More alliance soldiers were locked in heavy fighting with the Taliban in the west hoping to cut a key supply line to the town.

Some reports suggested the Taliban foreign minister had in fact defected in the face of mounting pressure and was now in the Gulf. But sources in Pakistan confirmed he had returned to Kabul and said there was still no clear rift in the ultra-Islamic regime.

Instead, the offer appears to indicate that Pakistan is applying pressure on moderate Taliban elements to negotiate their way out of the crisis.

Pakistan has made clear that it wants the bombing campaign to be brief and that it does not want the Northern Alliance, backed by its arch-enemy India, to sweep to power in Kabul. Gen Musharraf said publicly yesterday that he wanted to see "moderate Taliban" in the next Afghan government.

Pakistan was intricately linked to the emergence of the Taliban as a military force and has closely backed the movement financially and diplomatically. Pakistan is now the only country to maintain diplomatic links with the ostracised regime.

The Taliban have offered to hand over Bin Laden before but only if sufficient evidence was presented. Bin Laden is wanted both for the September 11 attacks and for masterminding the bombings of two US embassies in East Africa in 1998 in which 224 people were killed. He is also suspected of involvement in other terrorist attacks, including the suicide bombing of the USS Cole in Yemen last year.

But until now the Taliban regime has consistently said it has not seen any convincing evidence to implicate the Saudi dissident in any crime.

"Now they have agreed to hand him over to a third country without the evidence being presented in advance," the source close to the military said.

However, it is unclear whether the Taliban would have the ability to seize Bin Laden and hand him over.

The US administration has not publicly supported the idea of a trial for Bin Laden outside America and appears intent on removing from power the Taliban leader Mullah Mohammed Omar and the hardliners in the regime.

Some in Pakistan have suggested Saudi Arabia as a loca tion for any trial for Bin Laden. "The Pakistan army would be supportive of anything with a Saudi link," said the source.

The Saudi royal family has long seen Bin Laden as a threat because he has accused the government of corruption and mismanagement and continually demanded the withdrawal of US troops from Saudi soil.

Mr Muttawakil's clandestine visit to Pakistan was planned several days in advance. The Taliban ambassador in Islam abad, Mullah Abdul Salam Zaeef, left the embassy on Friday and travelled to Kandahar, home of the Taliban headquarters in southern Afghanistan, for talks with Mullah Omar to prepare for the visit.

It is not clear how the Taliban foreign minister travelled from Kabul to Pakistan without approval from the US. One report in the US yesterday suggested that Pakistani intelligence flew him out of the country in a small aircraft.