African and Asian countries are being urged to make a final push to wipe out polio, a crippling virus that afflicts young children.

The World Health Organisation, along with the United Nations Children's Fund (Unicef), have written to 30 nations saying that success hinges on their efforts.

In their letter, Dr Brundtland and Unicef executive director Carol Bellamy appealed in particular for truces to be organised in war zones so that children can be vaccinated.

Launching a World Health Organisation (WHO) campaign "Final Push for Polio Eradication in Year 2000" in New Delhi, Dr Brundtland said the world was on the verge of a major public health breakthrough.

"If we fail now, we fail the world's children," she said.

Appeal for truces

"The goal will become much more elusive, much harder and more expensive to achieve," she said.

Polio has been wiped out in North, Central and South America, Europe and the Western Pacific region as well as much of the Middle East and most of northern and southern Africa.

But it remains active in sub-Saharan Africa and south Asia. India, which has substantially stepped up vaccination campaigns, accounts for 70% of the remaining known cases.

It is particularly difficult for health organisations to administer polio vaccine in the conflict zones of Africa, such as Angola and the Democratic Republic of Congo.

Dr Brundtland said that in DR Congo, health workers continued to vaccinate children even though an immunisation ceasefire had temporarily broken down.

Polio is an infectious virus which causes paralysis and even death. There is no cure, but, given a few drops of vaccine, children can be protected for life.

Wiped out

The number of cases recorded annually has now dropped to just over 5,000 from more than 350,000 when the campaign of mass vaccinations started in 1988.

The campaign concentrates on mass vaccinations, or National Immunisation Days (NIDs), which aim to vaccinate every single child in a specific population on two separate days, one month apart.

The cost of the campaign is put at a $1bn and the WHO says there is currently a shortfall of £300m.

A BBC science correspondent says it remains to be seen whether polio really will be eradicated by the end of this year.

But, he says, the WHO is confident that it will soon be the second disease to be totally wiped out - joining smallpox in the pages of medical history.