WASHINGTON: The world's largest meeting on HIV/AIDS opens Sunday in the US capital with calls to speed up the global response to the three-decade-long epidemic that killed 1.5 million people last year.

The 19th International AIDS Conference is expected to draw 25,000 people, including politicians, scientists and activists, as well as some of the estimated 34 million people living with HIV who will tell their stories.

Among them is the only man who has achieved a functional cure of HIV though a bone marrow transplant, American Timothy Brown, who is scheduled to appeal for a fresh push toward a cure during the six-day conference that runs through July 27.

Other high-profile appearances include Secretary of State Hillary Clinton, former president Bill Clinton, former first lady Laura Bush, singer Elton John, philanthropist Bill Gates and actress Whoopi Goldberg.

President Barack Obama has faced some criticism for his decision not to attend in person. He is sending a video message and will invite some attendees to the White House for talks on Thursday, a top health official said.

Held every two years, the conference - whose theme this year is “Turning the Tide” - is returning to the United States for the first time since 1990, after being kept away by laws that barred people with HIV from traveling to the country.

The US ban was formally lifted in 2009, and researchers have described fresh optimism in the fight against AIDS on several fronts. Deaths and infections are down in the parts of the world most ravaged by the disease, while the number of people on treatment has risen 20 percent from 2010 to 2011, reaching eight million people in needy countries.

However, this is only about half the people who should be on treatment worldwide, signaling that much more remains to be done.

More than 34 million people worldwide are living with HIV, a higher number than ever before, and around 30 million have died from AIDS-related causes since the disease first emerged in the 1980s, according to UNAIDS.

Advances in antiretroviral medication have transformed the disease from a death sentence into a manageable condition for many sufferers, and may offer new paths toward prevention according to recent research.

But there remains a major gap in the United States between the number of people diagnosed and the number with their viral load under control through medication, a phenomenon known as the “treatment cascade.”

Even though 80 per cent of people with HIV in America are aware of their status, just 28 per cent have the disease under control. The hunt for a cure, which has eluded scientists, will be another hot topic.

HIV co-discoverer and Nobel laureate Francoise Barre-Sinoussi announced on Thursday a new roadmap for scientists in research toward a cure.

And Brown, also known as the “Berlin patient,” will address the conference on Tuesday at 1500 GMT to publicize new efforts in this direction.

Funding is at a critical juncture, with many nations boosting their domestic spending on the disease while international donations remain flat.

Total worldwide investment in HIV was $16.8 billion last year, an 11 per cent rise from 2010, but still far short of the $22-24 billion needed by 2015, according to a UNAIDS report released Wednesday.