The Bill & Melinda Gates Foundation gave $750 million Thursday to the Global Fund to Fight AIDS, Tuberculosis and Malaria to help assure that the organization can keep supplying AIDS drugs while it seeks to adjust to the economic downturn.

The Global Fund, which has disbursed $15.1 billion to low-income countries in the past decade, said in November that it would not award any new grants until 2014. Nearly all of the fund’s money comes from governments in the industrialized world, many of which were unwilling to increase their donations or, in a few cases, fulfill previous pledges.

The fear has been that some AIDS programs in Africa might run out of money, forcing patients to stop taking the antiretroviral drugs that are keeping them alive.

“These are tough economic times, but that is no excuse for cutting aid to the world’s poorest,” Bill Gates said in announcing the contribution at the World Economic Forum in Davos, Switzerland. His foundation had previously contributed $650 million to the fund over a decade.

A fund spokesman, Andrew Hurst, said the Gates donation will pay for 164,000 people to continue receiving AIDS drugs, buy 11.4 million bed nets and treat 427,000 cases of tuberculosis if their costs remain what they have averaged since the fund’s inception.

Also in Davos, former Japanese prime minister Naoto Kan said his country would contribute $340 million to the fund this year. Two years ago, Japan contributed $200 million, but it gave only $110 million last year because of domestic needs from the earthquake and tsunami. The latest is intended to be a catch-up contribution.

The announcements come two days after Global Fund director Michel Kazatchkine, a French physician, unexpectedly stepped down after five years. His leadership had come under criticism from some quarters. In November, the fund’s board announced that it would appoint a general manager to help run the organization, which has its headquarters in Geneva.

Kazatchkine, who has held various roles since the fund’s creation 10 years ago this month, said he concluded that “I should not continue as executive director in these circumstances.”

In addition to paying for antiretroviral drugs for 3.3 million people, the Global Fund has underwritten 8.6 million tuberculosis treatments and provided 230 million insecticide-treated mosquito nets for the prevention of malaria. During its existence, the fund has paid for 1,042 programs in about 150 countries.

The President’s Emergency Program for AIDS Relief, run through the State Department, helps pays for antiretroviral therapy for about 3.9 million people. As with the Global Fund’s beneficiaries, most of those people are in sub-Saharan Africa. The United States is also the largest donor to the fund, with $5.8 billion contributed to date.

Global Fund grants run for two years and can be renewed for three more if the programs are judged to be performing well. Some programs from the fund’s early years have exhausted five years of support and begun the process again; others have been taken over by national governments and no longer need the fund’s help.

The fund’s director of external relations, Christoph Benn, said that when the Gates donation is added to the $10 billion on hand and pledged from other sources for 2011 through 2013, there “should be enough” money to keep all worthy programs running uninterrupted.

Joanne Carter, a former member of the Global Fund’s governing board and head of the anti-poverty organization Results, said she and other advocates are calling for an emergency “replenishment” meeting before the global AIDS conference meets in Washington in July.

She said she hopes the meeting will raise $1.5 billion in new pledges from countries, enough to fund a new round of grants.