Obama extolled progress made since international health authorities began observing World Aids Day 20 years ago, when "widespread ignorance and fear" hampered efforts to educate people about AIDS' devastating impact on families and communities.
Thanks to the work of official, non-official and faith-based institutions, he said, "women in Kenya who were widowed by the disease and once shunned by society, have banded together to support and empower each other.
"Scientists around the world are discovering and engineering new medicines to give people with HIV/AIDS another chance at life ... And world governments are coming together to address the humanitarian crisis the pandemic has left in its wake.
Speaking before the Saddleback Church Civil Forum on AIDS, Obama thanked outgoing US President George W. Bush "for his leadership in crafting a plan for AIDS relief in Africa" and providing funding to prevent the spread of the disease.
Bush on Monday announced that his President's Emergency Plan for AIDS Relief had already met its goal of helping to treat two million people living with HIV/AIDS by the end of 2008.
Obama said the administration he will be leading when he takes over the White House on January 20 "will continue this critical work," but would go one step further.
"We must also recommit ourselves to addressing the AIDS crisis here in the United States with a strong national strategy of education, prevention and treatment, focusing on those communities at greatest risk.
"This strategy must be based on the best available science and built on the foundation of a strong health care system," he added.
Obama admitted, however, that "in the end, this epidemic can't be stopped by government alone, and money alone is not the answer either."
He asked all Americans to "do our part," and urged people to take inspiration from this year's World Aids Day slogan "Stop AIDS, Keep the Promise."
About two-thirds of the world's HIV-positive cases are in sub-Saharan Africa. At least one person in 10 lives with HIV in nations such as South Africa, Zimbabwe, Botswana, Lesotho, Malawi, Mozambique, Namibia, Swaziland and Zambia, the IFRC said in a June report.