Tens of thousands of children have been orphaned by the HIV pandemic
The US is set to spend $50bn to battle HIV/Aids in the next five years.
The US House of Representatives has passed a bill to more than triple government spending in Africa and other badly affected parts of the world.
The bipartisan measure, which is backed by the White House, was passed by 308 votes to 116.
The bill marks a huge increase from the $15bn authorised during the first five years of an initiative launched by President Bush in 2003.
"There is a moral imperative to combat this epidemic," said Nancy Pelosi, the House's Democratic speaker.
The initiative would be the largest US investment ever against a single disease.
Last May, Mr Bush asked Congress to set aside $30bn for the plan, aimed at providing treatment for 2.5 million people and preventing more than 12 million new infections.
The programme currently supports life-saving treatment for nearly 1.5 million people, the White House said.
Initially focused on Vietnam, Guyana, Haiti and 12 African nations, the programme will be expanded to include Malawi, Swaziland and Lesotho as well as some Caribbean nations.
Opponents of the bill argued that it was too expensive, and that more pressing needs closer to home needed to be addressed.
The UN estimates that two-thirds of the 33 million people infected with the human immunodeficiency virus (HIV) - the virus that causes Aids - live in sub-Saharan Africa.