The World Health Organization reported Saturday that an estimated 440,000 people with AIDS in developing countries are receiving life-extending drugs, well short of the 500,000 it hoped would be receiving treatment by now. Its goal is to put 3 million people on such medications by 2005.

The target of 3 million represents half the estimated 6 million people in developing countries who will probably die within a year or two if they do not receive antiretroviral drugs. Movement toward the goal has been "disappointing," the report said. At the current rate, the target will not be reached until about 2009.

A shortage of trained health care workers is one of the biggest obstacles to getting people into treatment, according to U.N. officials.

But U.N. officials insist that the goal can still be met.

The report was released on the eve of the 15th International AIDS Conference, which opens Sunday in Thailand. The theme of the conference, Access for All, reflects the organizers' concern that despite the progress made in making drugs more affordable many people are still not getting treatment.

The price of AIDS medicines has fallen to as low as $140 per person for a year's supply, and more governments and organizations are funding treatment. But developing countries face a challenge in training health care workers to ensure that patients not only take the drugs but also stay on them, and to monitor their condition and prevent further spread of infection.

"We have to be frank and admit that there's a long way to go," Peter Piot, executive director of the Joint United Nations Program on HIV/AIDS, an umbrella group of U.N. agencies that includes the World Health Organization, said at a news conference here.

According to the WHO, 15,000 health care workers in developing countries have been trained since 2001 to provide antiretroviral treatment; the goal calls for training 100,000 by 2005, U.N. officials said.

Reaching those numbers is difficult in part because people who receive training are often lured overseas by higher salaries. According to a report by the U.S. Agency for International Development, only 360 of the 1,200 doctors trained in Zimbabwe in the 1990s now practice in the country. In South Africa, which produces about 1,000 registered pharmacists a year, 600 pharmacists emigrated in 2001.

In Malawi, according to a World Bank AIDS official, only seven of 309 recently trained nurses studied had chosen to work in the public health care system, the most likely vehicle for getting antiretroviral drugs to the country's 900,000 HIV-positive people.

But U.N. officials said that some progress had been made. Perhaps the biggest strides have been in streamlining the drug regimens and reducing their prices, once the symbols of how unreachable antiretroviral treatment was for infected people in the developing world.

Five years ago, a year's supply cost $10,000, and a patient had to take more than a dozen pills a day. Today, the drug therapy often costs less than $200 a year and comes in fixed-dose combination pills, single tablets containing three different drugs that are taken once or twice a day.

But unless more health care workers are trained to administer the drugs, improved access to the medicines may actually pose a threat to patients, an AIDS expert said.

"That's a serious concern when you're dealing with drugs that are very toxic," said Kevin Frost, director of Treat Asia, a program of the American Foundation for AIDS Research. "If patients are self-medicating without proper supervision, it can very quickly lead to drug resistance and side effects, which if they are not managed, can be deadly."

U.N. officials said programs in many countries are on the verge of enrolling large numbers of patients in the next few months. In numerous countries, the basic infrastructure for treatment, health care clinics and workers, is in place but not being used effectively.

Jim Yong Kim, the director of AIDS programs for WHO, said: "It's just a matter of getting down to it, of going forward and getting people trained."

Since WHO announced what it calls the "three by five" program target in December -- 3 million people by 2005 -- only 40,000 people have been placed on AIDS drugs, officials said.

The figure of 440,000 on the life-extending drugs is an estimate derived from the reporting done by the countries themselves. It does not reflect the people who drop out of treatment.

Brown reported from Washington.