UN Secretary General Kofi Annan has attacked the US for failing to deliver enough funds to tackle Aids worldwide. In an exclusive interview with the BBC, he said the fight against terrorism was overshadowing the HIV/Aids epidemic. He expressed disappointment that the US and Europe were not doing enough to help the UN's global Aids fund. But President Bush's Aids adviser said the criticism was unfair, as the US was by far the biggest contributor to the campaign to tackle and prevent Aids. Mr Annan who is attending the International Aids Conference in Bangkok, issued a diplomatic rebuke by singling out Washington for being slow to deliver on its promises. He expressed disappointment that some of the $15bn earmarked by President George W Bush to tackle HIV/Aids was not yet going to the global fund - the body set up to raise money for Aids programmes. "The global fund is ready to go. If individual governments begin to set up their own initiatives, they start from scratch, it takes longer, the money that they hold will not be spent for a long time," he said. Mr Annan said he had hoped the US could at least contribute $1bn a year through the global fund, with the EU putting in another $1bn. With additional resources raised elsewhere, "the fund could have assured and sustained support through the next five years or so," Mr Annan said. He said he believed Mr Bush was concerned about the impact of Aids, but said it was now time to step forward and commit resources to that fight. But Dr Anthony Fauci, President Bush's senior adviser on Aids, said the decision to distribute funds mainly bilaterally reflected initial concern on how the global fund would be managed. "At the time the global fund was starting to get rolling, there was a concern on the part of the United States that if they put in this massive amount of money, $15bn, they wanted to have much more of a direct say in how it was spent," Dr Fauci said. The secretary general's frustration was evident in his direct and frank comments, says the BBC's Karen Allen who interviewed him. At a time when millions of dollars are being put into the fight against international terrorism, where, Mr Annan asked, is the "international solidarity" on Aids. He said the priority now was to move forward, commit more funds, and show leadership - from politicians, private business and the wider community. On the issues being discussed at the Aids conference here in Bangkok, Mr Annan said he was distraught about what he called the false debate on whether abstinence or condom use was the best way to prevent the spread of the disease. He said both sides of the argument shared the same objective - to get infection rates down - and it was skewing the issue. Anita Tiessen, deputy director of Unicef, told the BBC: "There has not been enough money, but more importantly there hasn't been enough political leadership. "It is a complicated disease, and it is complicated to prevent it because it is about sexual behaviour. "One of the most critical issues is that children are really being affected. We expect that by the end of the decade there will be 25m children who are orphans because their parents have died of Aids. "These are children who are then not getting an education, possibly having to raise their younger siblings, and very, very much at risk of exploitation by prostitution or trafficking."