The United States has pledged $334 million to global efforts to combat bird flu - the largest single pledge of any nation at a donor conference that ended in Beijing.
Officials attending the two-day conference say pledges totaled nearly $2 billion, exceeding the initial target of $1.2 billion to boost preparations to combat the H5N1 bird flu virus.
American delegation leader Ambassador Nancy Powell said the U.S. pledge will go mainly to Southeast Asian nations, especially Indonesia, Vietnam, Cambodia, and Laos.
"We announced our contribution today to the global effort against avian and human influenza of $334 million," said Powell. "The bulk of that is going to go into bilateral programs and technical assistance."
The second largest donor is the European Union, which pledged $120 million. China, as a conference co-host, pledged $10 million.
Organizers said the urgency for nations, especially poor ones, to prepare for a possible human pandemic is growing. Four fatalities in Turkey this month, the first outside of East Asia, brought the death toll to about 80 since 2003.
U.S. officials said some of Washington's contribution would also go to Turkey and some unspecified African countries.
Delegates said the U.S. pledge would fund bilateral programs and not go into a common trust, as proposed by the hosts of the donor conference.
Earlier, Chinese Premier Wen Jiabao called for the donations to the fund to be largely unconditional.
The Chinese leader called for enthusiastic donations and said China supports the establishment of a multilateral aid fund without extra conditions attached for nations, such as his own, that are aid recipients.
U.S. officials said they would ensure that bilateral programs are carried out in close consultation with the governments of recipient nations and international agencies such as the World Health Organization and the Food and Agriculture Organization.