Bill Gates, the chairman of computer software giant Microsoft, has pledged $750m to the troubled global AIDS fund during an annual meeting of the World Economic Forum (WEF) in Davos, Switzerland.
Gates, who spoke at the forum on Thursday, urged governments to continue to support the fund and save lives, despite the current economic downturn.
"These are tough economic times, but that is no excuse for cutting aid to the world's poorest," he said. "The Global Fund is one of the most effective ways we invest our money in every year."
The new commitment is in addition to the $650m that the Bill and Melinda Gates Foundation, which Gates founded with his wife, has already contributed since the Global Fund to Fight AIDS, Tuberculosis (TB) and Malaria was launched 10 years ago at Davos, according to a statement.
The public-private organisation, which has the backing of celebrities such as rock star Bono, accounts for about one quarter of international financing to fight HIV and AIDS, as well as the majority of funds to fight TB and malaria. But it has been forced to cut back and said last year it would make no new grants or funding until 2014.
The contribution from Gates came on the second day of the forum, which opened on Wednesday with a keynote address from Angela Merkel, German chancellor, that focused on Europe's economic crisis.
Germany is determined to play a full part in combating the eurozone crisis but will not commit to anything that it cannot deliver, Merkel said.
She questioned the rationale of those in financial markets, governments and the International Monetary Fund which were pressing Berlin to put more money on the table, but did not rule it out
"We have said right from the start that we want to stand up for the euro, but what we don't want is a situation where we are forced to promise something that we will not be able to fulfil," she said.
"If Germany, for example, on behalf of all the other member countries, were promising something that, if the markets really attack us we would not be able to come up with, then we have indeed an open flank."
About 40 heads of government, including Merkel and David Cameron, the British prime minister, are attending the event to discuss issues ranging from the eurozone crisis to Iran's nuclear programme and other issues.
Klaus Schwab, the founder and organiser of Davos, said this year's meeting would focus on how to develop a new world model as "capitalism in its current form, has no place in the world around us".
Leaders from the world's biggest 1,000 companies are participating in the WEF, which requires an annual membership fee of $45,000.
About 5,000 Swiss soldiers have been mobilised to provide security over the course of the gathering while the airspace over the exclusive resort has been severely restricted.
A small group of anti-capitalist activists have made their way to Davos as well, building a protest igloo.
Half a dozen demonstrators appeared briefly outside the security perimeter on Tuesday, painting anti-capitalist slogans in the snow.