The Global Fund to Fight AIDS, Tuberculosis and Malaria, which underwrites AIDS treatment for about half the people getting it in developing countries, announced Wednesday that it will make no new grants for the next two years because of the worldwide economic downturn.

The Geneva-based organization says it will continue to support about 400 AIDS treatment and prevention programs in more than 100 countries for now, but it will not pay for them to add patients or increase services.

“We cannot at the moment encourage in good faith an expansion of these programs,” Christoph Benn, the fund’s director of external relations, said Wednesday after a two-day meeting in Ghana of the board’s directors.

The decision comes at a time of growing clamor to scale up AIDS treatment in countries hardest hit by the disease, especially nations in sub-Saharan Africa.

A study earlier this year showed that treating infected people with antiretroviral drugs cuts their chance of transmitting the virus by 96 percent — leading to calls for a “treatment-as-prevention” strategy against the epidemic.

Other research has shown that adoption of circumcision by African men and more aggressive treatment of HIV-infected pregnant women can also drive HIV incidence down steeply. In a speech three weeks ago, Secretary of State Hillary Rodham Clinton said an “AIDS-free generation . . . is possible with the knowledge and interventions we have right now.”

With the Global Fund standing pat, that goal will be much more elusive.

The Global Fund has dispensed about $15 billion since its creation in 2002, including $2.8 billion this year. Nearly all of its money comes from Western industrialized countries, with the United States by far the largest donor. The money is distributed in competitive grants to health ministries and charities in needy countries.

About 14.2 million people in low- and middle-income countries, mostly in Africa, qualify on medical grounds for treatment with antiretroviral drugs. At least 6.6 million are now getting that treatment, with the Global Fund paying for the care of about 3.2 million people. A similar number are supported by the U.S. government through the President’s Emergency Plan for AIDS Relief (PEPFAR), created by President George W. Bush in 2003.

The fund needs $7 billion to pay for grants already awarded and has pledges to cover them. The European financial crisis, however, has cast an ominous shadow across this funding stream.

Italy, a big supporter in the early years, pledged to pay 130 million euros a year in 2009 and 2010 but has not made either payment. Spain pledged $200 million in 2010, but it ­reduced its contribution to $134 million and has not pledged anything for 2011, 2012 or 2013, according to Andrew Hurst, a Global Fund spokesman.

Matthew Kavanagh of Health GAP (Global Access Project), an advocacy organization in New York, called the Global Fund’s decison “irresponsible and reckless.” He characterized the amount of money needed to continue expansion of AIDS treatment as “a rounding error in the budgets of wealthy donor nations.”

The Global Fund’s 20-member board of directors prefers to make decisions by unanimous consent, but it had a split vote on this one, said one person who witnessed it.

“It was a very difficult and contentious decision,” said Jo­anne Carter, who heads Results, a group that lobbies for better AIDS and tuberculosis treatment in the developing world. She attended the meeting as a member of the delegation representing non­governmental organizations from developed countries.

“It’s a huge issue for countries, which see this next period of time as absolutely critical in terms of scale-up,” Carter said. She also said the decision sends the wrong signal to developing nations “in terms of encouraging their own ambitions” to more aggressively confront the epidemic.

The board’s decision reflects the grim recognition that its greater responsibility is to people already in Global Fund-funded programs who might die if the money ran out or was switched to other purposes.

“We do realize we have a very strong obligation to support these programs,” Benn said. “We can guarantee that programs that are currently running will continue.”

The fund’s directors also decided that China, Russia, Mexico and Argentina will no longer be eligible for Global Fund grants because they can afford to pay for the health programs on their own.

Grants are made for two years, with the possibility of extension for another three if performance benchmarks are achieved. At the end of the five years, however, a program can begin the process again — effectively making the Global Fund the permanent paymaster for state-of-the-art AIDS and tuberculosis therapy in places where that would be otherwise unaffordable. In all, 54 percent of the fund’s spending has gone to AIDS programs, 29 percent to tuberculosis and 17 percent to malaria.

In August, the fund solicited applications for new programs, the 11th round in its 10-year existence. The deadline for applications was to be March 2012, and about 90 countries were expected to submit requests for money. That round has now been canceled.

The United States is spending about $6.1 billion on overseas AIDS programs this year. Most of the money for antiretroviral treatment is delivered through bilateral agreements between the United States and recipient countries, often with universities and large charities acting as intermediaries.

Of that total, however, $1.05 billion went directly to the Global Fund for use in its awards. The Obama administration is seeking $1.3 billion for that purpose next year, although many observers say the fund will be lucky if Congress keeps the contribution at the old level.

In addition to paying for AIDS testing, treatment and prevention programs, the Global Fund over its lifetime has financed 8.2 million courses of tuberculosis treatment and the distribution of 190 million insecticide-treated mosquito nets for people to sleep under in malaria-endemic areas.