US Health Secretary Tommy Thompson, board chairman for the Global Fund to Fight Aids, TB and Malaria, said on Wednesday that the funding deficit could be as much as $800 million.
He said: “We will be short. It’s obvious that we all need to do a little bit more because we do not have enough dollars this year to meet our commitments.”
Hopes of major new pledges from Europe were expected after US president George W Bush promised $15 billion to fight Aids over five years.
But the hopes were dashed when the European Commission made it clear at an AIDS conference in Paris this week that it would not be putting new cash on the table.
The refusal came despite calls from hundreds of activists, and former South African president Nelson Mandela, for western countries to do more.
Activists say the developed world needs to prove its commitment to Aids by finding the money quickly.
Failure to come up with the money, they say, will prove the West does not care about diseases of poverty.
Scientists have also pressed for action, circulating a petition at the Paris conference calling for money to make the drugs they have designed available to all.
Lucy Matthew, European director of DATA, the African advocacy group founded by rock stars Bono and Bob Geldof, said the EU decision was pitiful.
She said: “There is still time for Europe not to lag in the fight against AIDS. But they have to believe in their hearts that this is an emergency.”
The Global Fund to Fight Aids, Turberculosis and Malaria has committed $1.5 billion to programmes in 92 countries in the last 18 months.
However, despite the Global Fund having pledges of $4.6 billion through to 2008, less than a quarter of its needs to the end of 2004 will be met by these promises.