UN Secretary General Kofi Annan has accused some countries of putting their "heads in the sand" in failing to spell out the truth about Aids.
Kofi Annan: "You need to call a spade a spade"
He told the BBC he was disappointed a declaration at a UN Aids conference did not specify homosexuals, prostitutes and drug addicts were at risk.
But Mr Annan still said the declaration was better than he had expected.
The declaration commits countries to work towards universal access to Aids care by 2010.
It also recognises the fight against the disease will cost $23bn (£12bn) by then, but does not specify how this will be raised.
'Silence is death'
Mr Annan said he would have preferred a clearer message.
"You need to call a spade a spade," he said.
"You cannot deal with a problem without confronting the issue of the most vulnerable who need assistance most. It's counter-productive. It's like putting your head in the sand and saying I don't want to know."
Mr Annan accused the African and Middle Eastern leaders who kept references to homosexual men, prostitutes and drug users out of the final declaration of being short-sighted.
The secretary general said politicians had to show more leadership because, on this issue, silence was death.
The UN declaration emphasises sexual abstinence, fidelity and condom use as the best ways to tackle Aids.
UN officials said the declaration referred to the importance of empowering women and girls, and used detailed language on prevention, including specific references to male and female condom use.
Certain countries frowned upon that terminology for fear of promoting promiscuity.
Some activists were furious that vulnerable groups were being rendered "invisible".
Aditi Sharma, HIV/Aids co-ordinator for ActionAid International, said: "It is incomprehensible how negotiators could come up with such a weak declaration when we needed urgent action to stop 8,500 people dying and 13,500 people from becoming infected every day."
UNAids says Aids has killed more than 25 million people since it was first recognised in 1981.
It estimates that 38.6m people are living with HIV worldwide.