The World Health Organization laid out its strategy to promote the use of DDT to combat malaria more aggressively, and called on countries where malaria is transmitted to develop specific plans for spraying walls and other surfaces inside homes.

The long-awaited announcement follows moves by the U.S. government and others to rely more heavily on pesticide spraying as other means of controlling malaria have proven inadequate to control the devastating disease. Malaria, a mosquito-borne disease eradicated decades ago from developed countries, infects as many as 500 million people a year and kills more than a million of them -- mostly children under five in sub-Saharan Africa.

While the United Nations health agency already had DDT on a list of approved chemicals, it hasn't actively promoted indoor spraying with DDT for more than 20 years. Instead, it has focused on other prevention methods, such as insecticide-treated mosquito nets.

But the agency said that research and testing have shown use of DDT in small amounts to be safe. Indoor spraying with DDT or other approved pesticides will now become a core part of the agency's malaria control strategy, along with promoting use of long-lasting mosquito nets and drugs to which the malaria parasite is not resistant, said Arata Kochi, director of WHO's malaria program.

"We must take a position based on the science and the data," Dr. Kochi said. "One of the best tools we have against malaria is indoor residual spraying."

While DDT is very effective, its use for malaria control alarms some environmental groups, which insist the pesticide poses dangers to humans and the environment. The Pesticide Action Network, a San Francisco group, disagreed with the WHO's stance that DDT is safe, insisting that the pesticide increases the probability of cancer and developmental delays in children.

In a speech Friday announcing the new plan, Dr. Kochi urged environmental groups who have expressed concern to "help save African babies as you are helping to save the environment."

The WHO said 10 countries in sub-Saharan Africa conduct indoor spraying programs using DDT; an additional four countries have spraying programs using other pesticides. The WHO recently worked with Tanzanian officials to develop a national spraying program for that country, and plans to meet with officials in Thailand next week, Dr. Kochi said.

The U.S. government welcomed the WHO's move, saying it expects to fund spraying programs, some of which would use DDT, in 15 countries. It funded the purchase of DDT for spraying in Zambia this year.

Sen. Tom Coburn, an Oklahoma Republican and physician who has pushed for more aggressive malaria control, called the WHO's clarified stance a "revolutionary document." "The junk science and stigma surrounding DDT -- the cheapest and most effective insecticide on the planet -- have finally been jettisoned," he said in a statement.