The United States insists it is leading the global fight against AIDS, despite stinging criticism of its drug and funding policies at a global conference.
Washington's moral agenda, trade policies and funding guidelines have come under attack from activists and world leaders, including French President Jacques Chirac and UN Secretary-General Kofi Annan.
But State Department spokesman Richard Boucher said the administration took the crisis very seriously.
"We do consider it the greatest threat of mass destruction on the face of the planet in the present age," he told reporters in Washington.
"And we are continuing our efforts to lead the efforts internationally with funding, with science, with diplomacy, and with the energy of the United States government behind it to try to address this crisis."
US AIDS czar Randall Tobias will set out Washington's commitment to fighting the pandemic, which has claimed 20 million lives and continues to infect 14,000 people a day, when he addresses the 15th International AIDS Conference later today.
Critics say Washington's bilateral effort undermines the UN-backed Global Fund to Fight AIDS, Tuberculosis and Malaria, which is facing a funding shortfall. The US is already the biggest donor to the fund.
Yesterday, the United Nations Secretary-General Kofi Annan, told the conference the United States should show the same commitment to AIDS it shows in the battle against terrorism.
Chirac, in a speech read out on his behalf, said a US drive for bilateral trade deals was undermining an international pact to provide cheap copycat AIDS drugs to the developing world and was "tantamount to blackmail".
The conference - the biggest gathering of scientists, activists, drug company bosses and AIDS sufferers - has seen daily protests against Bush, other G8 leaders and the drug industry for failing to do more to fight the pandemic.
The Bush plan has also drawn fire for linking funds to a policy of sexual abstinence over condoms, and requiring that drugs, purchased with US funds for use in developing countries, be approved by the Federal Drug Administration.