About 20,000 trained volunteers will vaccinate children under five from 25-27 October, the office of the UN co-ordinator for Afghanistan said.

The BBC's William Reeve: "Polio is a disease that mainly strikes children"

The youngsters missed two previous immunisation campaigns because of fighting.

The Taleban control more than 90% of the country, but are fiercely resisted by an opposition alliance in the north. Thousands have been killed and more than 150,000 displaced in the conflict.

Louis George Arsenault, the Unicef representative for Afghanistan, said that without a ceasefire in place "we might not be able to reach children in parts of four provinces".

Displaced hard to reach

Strict Islamic codes are enforced by the Taleban

The operation is particularly tricky in areas such as Darra Souf in the Samangan province, where the UN estimates about 35,000 people may be living in makeshift shelters and caves.

The ceasefire appeal followed a call by the UN Security Council on Friday for the warring parties to reach a political settlement and to ensure that humanitarian aid reaches all people.

The council also threatened the Taleban with limited sanctions if they do not hand over within 30 days the Saudi dissident Osama bin Laden for trial over last year's twin US embassy bombings in Africa.

Representatives of the Taleban and the US Government are due to meet on Monday to discuss the issue.

No polio by 2001

Polio is also being targeted in India, where the fifth annual Pulse Polio Immunisation programme was launched on Sunday in a drive to make the country polio free by the end of 2000.

About 130 million children were administered polio drops in a nationwide effort.

The government intensified the campaign by raising the age-group of children targeted from under-threes to under-fives.

Around 600,000 immunisation booths have been set up across the country.