A counsellor talks to HIV-positive former sex workers as children of the workers play in the background at the New Light Charitable Trust centre in Kolkata.
Some 550 representatives of sex workers from India and 41 other countries were attending the seven-day event in the eastern Indian city, organisers said.
"Sex workers wanted to be a part of the US conference to fight the challenge of HIV/Aids across the world," said Bharati De, secretary of the Committee for Coordination of Indomitable Women, which represents sex workers in Kolkata.
India's AIDS control programme has cut new HIV/AIDS infections by 50% in the last 10 years.
The country has an estimated 2.4-million people with HIV. One of India's key strategies has been to scale up preventive education campaigns among high-risk groups such as sex workers.
But despite the significant drop in fresh cases, India still has the highest number of people living with HIV after South Africa and Nigeria.
The Indian conference has been called the sex workers' "Freedom Festival".
The Kolkata meeting will deliberate on the "Seven Freedoms" – the right to move, work, have access to healthcare, participate, organise, be free of violence and discrimination – without which sex workers say they cannot reduce their vulnerability to HIV.
"Sex workers have decided to hold a parallel conference here in Kolkata to make their voices heard," Smarajit Jana, chairwoman of the Indian event, told AFP.
"We hope this conference will make sex workers' voices louder and stronger," Jana said outside the conference auditorium on the eastern fringes of the West Bengal state capital.
Held every two years, the International Aids Conference is returning to the United States for the first time since 1990, after being kept away by laws that barred people with HIV from travelling to the country.
Some 25 000 people, including celebrities, scientists and HIV sufferers are expected to attend the US conference which opens on Sunday to call for a jumpstart in the global response to the three-decade Aids epidemic.
The US conference runs until July 27.
But "the US government's travel restriction for sex workers will bar many of them from attending the conference," Andrew Hunter, president of the Global Network of Sex Work Projects, said in Kolkata.
"With the US now leading the fight for lesbian, gay and transgender equality, we are extremely disappointed they refuse to revise their restrictions on sex workers and refuse to recognise we're human beings with basic rights," he added.
Kolkata sex worker Bharati De said she was disappointed she could not go to Washington.
"The restrictions imposed by the US on granting visas to sex workers have dashed our hopes of sharing our opinions with others," she told AFP.
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. – Sapa-AFP