The United Nations Children's Fund has warned that a recent polio outbreak in Indonesia poses a global threat and says planned vaccination drives in the country are crucial to averting a crisis.

Indonesia reported its first outbreak of polio in nearly a decade last March. Since then, despite two immunization drives, more than 220 children have been infected.

The United Nations Children's Fund, or UNICEF, says another round of nationwide immunizations planned for August 30 and September 27 is aimed at reaching more than 24 million children.

David Hipgrave, UNICEF's head of health and nutrition, said Indonesia has the world's highest new case rate, and the reemergence of the water-borne disease poses a global threat.

"It's a looming problem not just for Indonesia but also globally," he said. "We are really on the cusp of eradicating polio globally. Many of the other countries in which the virus has been reintroduced have successfully combated that reintroduction, and the outbreak in these countries has been quashed. That's what we are trying to do with these next two rounds."

The Global Polio Eradication Initiative, spearheaded by UNICEF, the World Health Organization, the U.S. Centers for Disease Control and Prevention and the civic group Rotary International has caused polio cases worldwide to drop by 99 percent since 1988.

But the campaign suffered a setback two years ago, when many people in Nigeria refused to have their children vaccinated following false reports the vaccine could spread AIDS or cause sterility. Outbreaks then spread from Nigeria across Africa, the Middle East, and into Indonesia, infecting 16 countries that had been polio free.

UNICEF's Mr. Hipgrave says the planned massive immunization drive across Indonesia is crucial to stopping the spread of the disease.

Polio, which is carried in human waste, is highly infectious, and usually attacks children under the age of five. It attacks the nervous system and paralyzes or kills many victims.

"Every child across the country - more than 24 million - will be vaccinated with two drops of vaccine. There'll be 245,000 immunization posts," said Mr. Hipgrave. "It's an enormous effort, it costs a lot of money, and it involves a lot of people, and it really needs the highest level of support."

Two previous vaccination campaigns in May and June reached close to six million children each.