About 40 people climbed onto the platform at the Barcelona meeting while US Health and Human Services Secretary Tommy Thompson was speaking.

The protesters were criticising the amount being spent by the US government fighting Aids across the world.

They can shout, but that doesn't deter me or the president one bit

Tommy Thompson, US Health and Human Services Secretary

Some waved placards declaring "Wanted: Bush and Thompson for murder and neglect of people with AIDS".

Security officers shielded Mr Thompson from the protesters, who shouted "shame, shame" and blocked him from being seen by the audience.

Committed

Mr Thompson then left the platform and held a news conference behind the auditorium.

He later promised to meet the protesters to discuss their concerns.

Speaking to journalists, he said: "The United States is passionately committed to this international fight.

"I understand that people are passionate about this and want to blame the United States, but the United States under President Bush has doubled the amount of resources it provides for the fight against AIDS."

He added: "I understand that people want to yell and scream, but they would serve their cause much better... if they would help other countries see the light.

Mr Thompson defended US policy on Aids

"They can shout, but that doesn't deter me or the president one bit," he said.

Last month, President Bush announced a five-year $500m initiative to stem transmission of HIV from mothers to their children in Africa and the Caribbean.

More than 2 million women carrying the Aids virus give birth each year, and 90 percent of those pass it on to their young during pregnancy, childbirth or nursing.

Opposition

But critics said the initiative was "grossly underfinanced".

Aids activists complain that Bush is ignoring people already living with the disease.

They want the US Government to contribute more to the United Nations-backed Global Fund to Fight Aids, Tuberculosis and Malaria.

Over 15,000 doctors, politicians and campaigners are attending the XIV International Aids Conference in Barcelona, which continues until Friday 12 July.