The US Senate granted President George W Bush the massive funds he sought to take on the disease yesterday.
Senate majority leader Bill Frist, a doctor, hailed passage of the five-year plan as "the first major step in reversing this greatest of humanitarian challenges of the 21st century".
The bill passed by voice vote after the senate, at White House urging, defeated all but one attempt to amend the measure cleared earlier in the House.
House leaders agreed to the one amendment, on debt relief for poor AIDS-hit countries, and are expected to send the bill to the president as early as next Tuesday.
In a statement issued by the White House, Mr Bush said he looked forward to signing the legislation as soon as possible.
"With today's vote in the United States Senate, Congress has given the hope of life to millions of people in countries most afflicted by AIDS.
"This historic legislation will enable us to provide critical treatment and care for millions who suffer and greatly expand successful prevention programs to help those at risk," Mr Bush said.
Mr Frist and other leaders said it was imperative to get the bill to the president quickly so he can go to the June 1-3 summit of world leaders in Evian, France, with evidence of US determination to prevent the spread of AIDS and bring relief to its 42 million victims.
AIDS groups agreed that the US action could spur others at the summit to increase their investments.
Dr Peter Piot, head of the Joint United Nations Program on HIV/AIDS, said the congressional action would "send a strong message that the global fight against AIDS should be a top priority at this meeting".
Democrats chafed at resistance to their attempts to amend the legislation, but joined in stressing the need for unity and urgency.
HIV/AIDS, said senate Democratic leader Tom Daschle, is more than a humanitarian crisis.
"AIDS is a national security issue. It is a public health issue. It is an economic issue. And it is a moral issue. We have the tools to fight this disease. It is our duty and our obligation to use them," he said.
Mr Bush set the stage for the senate vote last January when he urged congress in his State of the Union speech to come up with $15 billion for worldwide AIDS programmes, nearly triple current levels of spending.
The legislation, while unprecedented in its scope, only authorises the spending of $15bn over five years. Congress must still approve real spending levels in its annual budget appropriations.
Failure of the president and congress to actually fund the program would be "playing a cruel joke on countries battling for survival", said Global AIDS alliance executive director Dr Paul Zeitz.
The bill targets 12 nations in sub-Saharan Africa, as well as Haiti and Guyana, that have been ravaged by the AIDS pandemic.
Mary Kanya, chairwoman of the African HIV/AIDS Task Force, thanked the US for its help when the world was "standing on the threshold of the extinction of the African people".