"This level of assistance is unprecedented and the largest commitment by any nation to combat a single disease in human history," Mr. Bush said.
Sharing the stage with an HIV-positive mother from Africa, Mr. Bush said "the generosity of the American people is one of the great untold stories of our time," CBS News White House correspondent Mark Knoller reports.
The money would provide treatment for 2.5 million people under the President's Emergency Program for AIDS Relief, Mr. Bush said.
Through March 31, the program has supported treatment for 1.1 million people in 15 countries, including more than 1 million in Africa, he said. The program's original five-year mandate, which called for spending $15 billion, expires in September 2008. Mr. Bush asked Congress to renew it.
"When I took office, an HIV diagnosis in Africa's poorest communities was usually a death sentence. Parents watched their babies die needlessly because local clinics lacked effective treatments," the president said.
White House press secretary Tony Snow said the specific goals for the next five years — after Mr. Bush leaves office — call for treatment of 2.5 million people, prevention of more than 12 million new infections and the care of more than 12 million people, including 5 million orphans and children.
The president said the money "this money will be spent wisely," in nations where it can have the greatest possible impact and be sustainable.
Mr. Bush also announced that his wife, Laura, will visit four African countries — Zambia, Mali, Mozambique and Senegal — that have benefited from the U.S. program and report back to him on her findings. The trip will take place June 25-29.
The president's announcement comes before next week's annual summit of industrialized nations in Heiligendamm, Germany. Germany is pledging to make Africa a central issue and is calling for more aid, further debt relief and improved financial oversight.