VIENNA (AP) -- World leaders lack the political will to ensure that everyone infected with HIV and AIDS gets treatment, the head of a meeting dedicated to the disease said Sunday.

Julio Montaner -- the president of the International AIDS Society and chairman of the AIDS 2010 conference -- said the G-8 group of rich nations has failed to deliver on a commitment to guarantee so-called universal access and warned this could have dire consequences.

"This is a very serious deficit," Montaner said. "Let's rejoice in the fact that today we have treatments that work ... what we need is the political will to go the extra mile to deliver universal access."

Montaner's comments to reporters appeared to foreshadow one of the key topics for the weeklong gathering, which organizers say has drawn 20,000 policymakers, experts and advocates to take stock of efforts to fight the disease and generate momentum for the future.

Reflecting the emotional nature of the debate, protesters carrying banners and shouting slogans such as "broken promises kill, show us the money!" and "treat the people!" delayed the start of the opening session.

In 2005, G-8 leaders committed in a communique to developing and implementing an Africa-focused package for HIV prevention, treatment and care with the aim of getting "as close as possible to universal access to treatment for all those who need it by 2010." They reaffirmed and broadened their commitment a year later in Russia with more detailed financing pledges.

But a G-8 accountability report from the most recent summit of world leaders in Canada last month acknowledged that the "universal access targets with respect to HIV/AIDS will not be met by 2010."

U.N. Secretary-General Ban Ki-moon, in a video address to participants, also weighed in on the issue.

"Universal access must remain our beacon -- access to lifesaving drugs, access to HIV prevention, treatment, care and support," Ban said.

"It is achievable, it can be done!" singer Annie Lennox said in her message to delegates.

Among the multitude of matters to be discussed by participants through Friday are the decriminalization of drug users, as well as the growing AIDS epidemic in Eastern Europe and Central Asia.

Montaner accused governments from some Eastern European states of indifference to the acute situations in their countries and said their absence at the Vienna meeting was "irresponsible to the point of criminal negligence."

According to the World Health Organization, 33.4 million people were living with HIV in 2008. While the numbers of deaths declined to 2 million in 2008 from 2.2 million in 2004, about 2.7 million new infections still occur each year.

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