The World Health Organization is warning that its global campaign to eradicate polio could end in failure because the northern Nigerian State of Kano is refusing to immunize its children against the disease.

The World Health Organization says polio is spreading from Nigeria to countries that already had wiped out this crippling disease. The latest victims are Benin and Cameroon. W-H-O says the polio virus is traveling across Nigeria's border into neighboring countries and is putting millions of children at risk.

The agency calls this a serious setback to its efforts to rid the world of polio by the end of 2005. When the global eradication campaign began in 1988, about 350-thousand polio cases were reported annually. Last year, that number was down to 667 cases.

W-H-O officials pin the blame for the resurgence of polio in west Africa on the refusal of some Islamic leaders in the northern Nigerian State of Kano to immunize their children. The leaders claim that the polio vaccine is contaminated with substances that can cause H-I-V/AIDS, cancer and sterility in women.

The World Health Organization denies this. It says the vaccines are safe, and recent tests of vaccines sent by the Nigerian government to W-H-O laboratories show they contain no infectious agents. Nigeria's president, Olusegun Obasanjo, agrees with the W-H-O.

In an effort to resolve this controversial issue, W-H-O has invited health ministers from affected countries to a special meeting in Geneva on Thursday. W-H-O says Nigeria's national health minister and a representative of the state of Kano have promised to attend.

W-H-O has spent more than four-and-one- half billion dollars since 1988 on the global campaign. If it succeeds, this would make polio only the second disease after smallpox to be eliminated from the world.

W-H-O says Nigeria has exported polio to at least six west African countries, including Benin, Burkina Faso, Cameroon, Chad, Ghana, Niger and Togo. Outside of west Africa, polio is present in only five countries -- India, Pakistan, Afghanistan, Egypt and Lebanon. Nigeria reported three-hundred cases of polio last year, nearly half of the world's total.