Saying that the failure to deliver AIDS drugs to impoverished people is so grave that it has become a global health emergency, the World Health Organization plans to provide such drugs to three million people, most of them in sub-Saharan Africa, by the end of 2005.

The number of people in these countries who would receive drugs under the W.H.O. plan would be nearly four times the total to be covered by 2005 under all existing programs. For example, President Bush's initiative calls for treating two million people in 14 countries by 2008.

W.H.O. plans to adapt many of the rapid response skills it learned in controlling the SARS epidemic and in responding to health emergencies in Afghanistan, Iraq and Liberia, said Dr. Jong Wook Lee, the United Nations health agency's director general. Dr. Lee is expected to announce the plan at a United Nations General Assembly meeting on AIDS today and to ask countries to appeal to his agency for help.

"From a public health perspective, we need to treat at least three million people by 2005 to avert an enormous catastrophe," Dr. Jim Kim, who is overseeing the AIDS treatment program as an adviser to Dr. Lee, said in an interview. "We cannot wait any longer."

If the 34 countries with the highest H.I.V. rates "each get 50 percent of those who require treatment into treatment by the end of 2005, we will reach 92 percent of our goal," Dr. Kim said.

One AIDS expert said that AIDS researchers had been discussing such an idea for two years. The health agency's goal is a good one, the expert said, but is unlikely to be met because "we lost two years from inaction." Still, the expert said, "we have to get on track, and even if we reach one to two million, that would be a huge success."

W.H.O., with a $1 billion annual budget, plans to add $100 million a year for the new initiative to the $50 million it already spends on AIDS as it appeals for more money from governments and other sources.

The plan comes two months after Dr. Lee became director general of W.H.O., which was criticized for its slow response to the early years of the AIDS epidemic. After turmoil within the agency over its commitment to fighting the disease, the United Nations created an agency, Unaids, under the direction of Dr. Peter Piot.

Dr. Kim said that W.H.O. will work with Unaids as well as governments and private organizations to provide countries with the technical expertise needed to deliver the drugs.

What is perhaps more significant than the amount of money being provided is the organization and the type of experience that W.H.O. has had working with developing countries.

The most optimistic projections from all existing antiretroviral programs are that they would reach 800,000 people in the third world by 2005, Dr. Kim said.

Dr. Lee has given Dr. Kim's team until Dec. 1, World AIDS Day, to develop standardized guidelines, including ways to help developing countries get quality antiretroviral medicines. The guidelines will also deal with simplified treatment regimens, laboratory testing for complications and rapid training for the thousands of health workers who will be needed to deliver the treatment.

W.H.O. has long held a high reputation for the quality of its scientific expertise in making recommendations that many countries, particularly those in the third world, follow closely to control diseases. But it had seldom been an action agency, like the United States Centers for Disease Control and Prevention, until W.H.O. coordinated the response to the SARS epidemic and declared it a global health emergency.

That experience taught W.H.O. the importance of acting quickly and that "we must change the way we think and change the way we act," Dr. Lee said. "Business as usual means watching thousands of people die every single day."

The overwhelming majority of H.I.V. infections are in sub-Saharan Africa, where women account for 58 percent of cases and the virus is spread predominantly by heterosexual intercourse. The disease is contributing to food shortages in that region and threatening progressive economic collapse.

Of the 42 million H.I.V.-infected people in sub-Saharan Africa, five million to six million urgently need antiretroviral treatment because their illness has advanced to AIDS, W.H.O. says. But "99 percent of the H.I.V.-positive people who need H.I.V. treatment today in sub-Saharan Africa do not have access to it," said Dr. Piot of Unaids.

After receiving an appeal for AIDS drug treatment, W.H.O. will dispatch a team to determine the ability of the government and private organizations to deliver the drugs.

W.H.O. has not determined which combination of drugs it will recommend. The agency usually makes such choices after years of deliberating over findings from large studies.

But in recommending antiretroviral regimens "we are just going to make a decision because we are working under emergency conditions," Dr. Kim said. "We have got to start with something and say this is it" and change later, if necessary.

"We will say, use this regimen for H.I.V. patients with tuberculosis, that regimen for H.I.V. patients without TB, and that is it for now," Dr. Kim said. Such decisions are important, he said, because generic drug manufacturers want to know which drugs to produce and how much.

World opinion has pressured manufacturers to lower the prices of antiretroviral drugs for developing countries to the point where the cost is less than a dollar a day. At the same time, studies in Africa have provided evidence that patients there are better at following their pill regimens than Americans, contradicting long-held prejudices.

A senior W.H.O. worker will lead the teams that go to the countries. Because the agency does not have enough people in its H.I.V. program, people who work with other diseases will lead some teams.

W.H.O. will also develop checklists to determine when a country is ready to start a treatment program.

"We hope that through this process with partners we will quickly develop an information base country to country that currently does not exist," in part by using teleconferences and the Internet as it did for the SARS epidemic, Dr. Kim said.

Because what works in one country may not work in another, "the antiretroviral treatment plans could look different in every country and maybe even in every village and every region," Dr. Kim said.

The agency has consulted Dr. Donald M. Berwick, president of the Institute for Healthcare Improvement in Boston, about ways to ensure quality control while expanding training and field programs.

Dr. Barry R. Bloom, the dean of the Harvard School of Public Health, said that "anytime health workers every Friday can analyze what went right and what went wrong so they can improve performance, it will benefit not only H.I.V./AIDS but also improve health care for everyone."

"Addressing H.I.V./AIDS in resource-poor countries will be the defining issue for W.H.O. and its new leadership," Dr. Bloom said.