The U.S. government, already the world's largest source of money to fight AIDS, faced demands on Monday from international AIDS officials, policymakers and activists to give a larger share to the Global Fund to Fight AIDS, Tuberculosis and Malaria, the main multinational fund to combat the disease.

The Bush administration has proposed annual payments of $200 million to the fund, an amount criticized by many, one of whom who said the United States should give the fund five times that much.

"It's profoundly inadequate," said Stephen Lewis, the U.N. special envoy for Africa. "It should be $1 billion a year, but it is only $200 million a year," he said, referring to Bush's budget request for the next fiscal year.

The calls for additional U.S. financial support to the Global Fund came as the United Nations reported on Monday a projected funding gap of 50 percent in the AIDS battle by 2007 -- $10 billion short of the $20 billion needed.

But U.S. officials at the 15th International AIDS Conference said that other countries should step up their contributions. A top U.S. official at the conference said the Global Fund, launched in 2002 with U.S. support, has shown success at raising money, but that much of the money is "just sitting there" waiting to be spent.

Only about $430 million of $3 billion in the fund have been disbursed, said the official, Randall L. Tobias, U.S. global AIDS coordinator. "We're certainly going to continue to contribute to the Global Fund, but more money this year would simply go into an account in the World Bank," he said.

"We need to put more emphasis on getting that money put to work," Tobias added. "Let's build the buildings that we've got the money for."

For next year, the Global Fund will need even more money -- $3.5 billion, said Richard Feachem, the fund's executive director. The fund helps pay for 300 projects in 130 countries. Feachem said that the disbursement rate depends on the speed at which recipients perform their work.

"The money follows the results," he said.

The need for such funding is crucial in Africa, Lewis said. "We're really on the knife's edge of the chasm," he said. In sub-Saharan Africa, about 25 million people are infected with HIV, the virus that causes AIDS, which amounts to 70 percent of the world's total. "Either we continue the flow of funds and continue to increase the treatment and make people feel there's hope, or we suffer a dreadful setback in responding to the pandemic."

The bulk of U.S. AIDS prevention dollars are destined for the five-year, $15 billion President's Emergency Plan for AIDS Relief, which aims to treat 2 million people with antiretroviral drugs and prevent 7 million new HIV infections over the next five years.

Despite its size and ambitions, the plan has been criticized. Complaints include the decision to limit aid to 15 countries; the promotion of AIDS-prevention strategies that emphasize abstinence; and the requirement that foreign-made generic drugs used in the program must be approved by the Food and Drug Administration.

Paul S. Zeitz, president of the Washington-based Global AIDS Alliance, a nonprofit organization, said the debate on funding priorities mirrors the Bush administration's approach to Iraq and global warming policy.

"This is a battle between a U.S. go-it-alone approach and multilateralism," he said.

Tobias said it was unreasonable to demand $1 billion or more as the U.S. contribution to the Global Fund. "That has never been anywhere on the horizon of anything the United States government has ever considered," he said.

He said there is a need for both the multilateral and the U.S. plan. He described the Bush administration's plan as building on 20 years of AIDS experience among agencies including the U.S. Agency for International Development and the Centers for Disease Control.

Mark Dybul, deputy chief medical officer for Tobias's office, said that President Bush's five-year plan disbursed $350 million in its first month of operation. "Within days of spending that money," he said, 300 rural Ugandans with AIDS were put on life-extending drugs.

However, despite claims that the president's plan is putting money to work quickly, in most cases the funds have been transferred from the U.S. Treasury to the bank accounts of grant recipients, based on interviews with grant recipients.

The recipients, in turn, are augmenting AIDS programs, or creating new ones, to put the money to use. For example, the Harvard School of Public Health received $17 million and the Mailman School of Public Health at Columbia University received $25 million in February -- the first installment of large, five-year grants from the presidential plan.

Although both universities have long-standing collaborations with African medical institutions, virtually all the details of where and how the money will be spent are still being negotiated, the schools' deans said in interviews last month. When a reporter asked to see a copy of Harvard's contract with the presidential plan, the university provided a sheet of paper listing the amount of the award, but with no description of the scope of work, a timetable, list of subcontractors or sites where the money would be spent.

Staff writer David Brown in Washington contributed to this report.

Protesters demonstrate at the 15th International AIDS Conference in Bangkok. The U.S. has pledged annual payments of $200 million to the main multinational fund to fight the disease.