Their country is in 'its most critical period'
He backs the reinstatement of the country's former king, Mohammed Zahir Shah, who is living in exile in Rome, as acting head of state.
The United Nations special representative for Afghanistan told the BBC that the country faced a new opportunity for peace which has not existed before.
The official, Lakhdar Brahimi, said there was unprecedented international support for a settlement to 30 years of conflict, even among neighbouring states that have supported one side or another in the war.
As a result of the international crisis surrounding the country, he said, "the Afghan people have an opportunity to at last get this 30 years of crisis behind them."
Interim plans
In Peshawar, delegates are discussing the formation of a broad-based multi-ethnic government and the composition of a 120-man interim council to oversee the transition of power and avoid a power vacuum.
But there are no significant members of the opposition Northern Alliance or moderate members of the Taleban present. Nor, despite being invited, have any representatives of the former king attended.
Pir Gailani told the meeting that Afghanistan had been "plunged into the most critical period of its history."
"Efforts should be made to stop the military operation and start work on reconstruction of the country as early as possible," he said.
He said that he and the former king, Zahir Shah, had agreed that a caretaker government under the king should take over from the Taleban.
"During the period of the interim government, a United Nations security force organised from Islamic countries should be deployed ...to maintain law and order," he added.
Pir Gailani, an ethnic Pashtun like the Taleban leadership, urged Taleban members who believe in peace and a broad-based government to break ranks.
"I consider their co-operation significant and fruitful," he said.
Most of those attending the meeting appeared to be Pir Gailani's supporters - an indication of the support he commands and a sign that he is likely to play a significant role in any future administration.
The BBC's Susannah Price, who is in Peshawar, suggests that while this is a start, there is a long way to go before any administration representing all ethnic groups and political beliefs can be agreed.
Afghanistan is made up of a patchwork of fractious tribes that throughout the country's history have fought for control.
It is unclear if any trust exists between leaders of the Northern Alliance, who are mainly Tajiks, Uzbeks and Hazara, and moderate members of the Pashtun tribe who back the Taleban.
Pakistan says some moderate Taleban representation should be included in any future government as Pashtuns make up the largest ethnic community.