"We are threatened with extinction," Botswanan President Festus Mogae, who is in New York for a three-day United Nations conference on HIV and AIDS, said Tuesday. "People are dying in chillingly high numbers. It is a crisis of the first magnitude."

Mogae, who has the dubious distinction of leading the nation with the world's highest rate of the virus that causes AIDS, is rallying a response of the highest order. An estimated 38.8% of Botswana's 1.5 million people are HIV-positive, according to a U.N. report, making the country the epicenter of the pandemic in Africa. But it also may be a model for the international response, as Mogae's government prepares to launch the most ambitious combination of prevention and treatment programs on the continent.

By the end of the year, the government hopes to begin treating with antiretroviral drugs as many as one-third of those with AIDS.

"We see before us the most dramatic experiment on the continent," said Stephen Lewis, a Canadian and the U.N. envoy to Africa. "If it succeeds, it will give heart to absolutely every country worldwide."

If the ambitious program could work anywhere in Africa, it would be Botswana. One of the smallest yet wealthiest countries in southern Africa, it boasts a well-educated population, a developed health-care program and, most important, a motivated president in a region where some leaders still deny the devastation of acquired immune deficiency syndrome.

Mogae admits that it took him too long to realize the scale of the crisis. Ignorance about AIDS allowed the disease to get a foothold, and it was quickly spread by migrating workers and the breakdown of social taboos that once mandated fidelity.

Now extreme measures are needed to deal with the disease. Since last year, Botswana has required that all foreign workers be tested for the human immunodeficiency virus, which causes AIDS, before entering the country. The government is planning a house-to-house survey in three towns to determine who needs care or more education about the disease. It is building special laboratories to handle wide-scale AIDS testing and is preparing an infrastructure to deliver drugs donated by pharmaceutical companies and others.

But along with the hope is the reality that stumbling blocks can trip up the best intentions.

Even when much-needed drugs are free, it doesn't mean that everyone can get them. In August, the Bill and Melinda Gates Foundation and Merck & Co. pledged $50 million each in a joint project to buy and administer anti-AIDS drugs. But the money still hasn't arrived, said Mogae, because his government and the donors have been bogged down in negotiations about procedures.

"Our attitude is, you help us do it, you don't do it for us," he said. "We will do what you ask, but we need to learn our own lessons."

One requirement of the donation is that Botswana be able to deliver and monitor the use of medicines. The government has developed a "buddy system," in which two patients work together to bolster compliance, but it is stuck on the foundation's demand that Botswana supply clinics with linked computers and refrigerated storage to ensure that the medicines are handled properly.

"Who is going to pay for it?" Mogae asked. "It hasn't been decided." In one of the more successful programs, the government provides free drugs to help prevent mother-to-child transmission of the disease and baby formula to reduce the passing of the virus through breast-feeding. Unlike similar programs in other African countries that limit treatment to the child, the mother and her partner in Botswana also can receive free care.

"If we can keep the parents alive for another five or six years, it doubles the chances of survival for the child. It is difficult to get men to agree to be tested, but we are beginning to get at them," Mogae said. "We tell them, 'If you take the medicine faithfully, you can raise your child.' "

However, some women are reluctant to accept canned formula because its use in villages where breast-feeding is the norm might reveal that the mothers are HIV-positive.

Sheila Dinotshe Tlou, who has been educating people in Botswana about AIDS since 1987 and was once called "a prophetess of doom," said that while previous education campaigns have targeted women, including men is important.

"We are teaching women to be more assertive--to be able to demand protection--but at the same time we are teaching men the basics," she said.

Most of all, it takes a whole community to make prevention and treatment programs work, especially when it comes to antiretroviral regimens. At least two pills must be taken daily without fail. A recent study suggests that missing just five of 100 doses dramatically reduces the drugs' effectiveness.

"I think of the problems we had to convince women to take birth control pills," Tlou said. "That's one lousy little pill once a day. I think of how mobile the people are. They are in the village one day and at the cattle post for a week. If they forget their hypertension pills, that's one thing. But think of antiretrovirals. If they don't adhere to the drug schedule, we'll have rampant drug-resistant viruses running across Africa.

"There is not much hope for the 300,000 [between the ages of 15 and 25] who are already infected," she said. "But now I can meet a 13-year-old girl and tell her, 'Listen to me, sister, and you will surely live.' "

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