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 has said.
Julio Montaner - the president of the International Aids Society and chairman of the Aids 2010 conference - said the G8 group of rich nations 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," Mr 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."
Mr Montaner's comments to reporters appeared to foreshadow one of the key topics for the weeklong gathering, which organisers said 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.
UN 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," Mr Ban said.
Among the multitude of matters to be discussed by participants are the decriminalisation of drug users, as well as the growing Aids epidemic in Eastern Europe and Central Asia.
Mr Montaner, in his comments to reporters, accused governments from some Eastern European states of indifference to the dire 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 Organisation, 33.4 million people were living with HIV in 2008.
While the numbers of deaths declined to two million in 2008 from 2.2 million in 2004, about 2.7 million new infections still occur each year.