* UNAIDS says ending AIDS is "entirely feasible"
* HIV drugs keep more patients alive, prevent new cases
* AIDS deaths at 1.7 mln in 2011, down from 2.3 mln in 2005
* AIDS still "one of world's most serious health challenges"
By Kate Kelland
LONDON (Reuters) - An end to the worldwide AIDS epidemic is in sight, the United Nations says, mainly due to better access to drugs that can both treat and prevent the incurable human immunodeficiency virus (HIV) that causes the disease.
Progress over the past decade has cut the death toll and helped stabilise the number of people infected with HIV, the U.N. AIDS programme said in its annual report on Tuesday.
"The global community has embarked on an historic quest to lay the foundation for the eventual end of the AIDS epidemic. This effort is more than merely visionary. It is entirely feasible," UNAIDS said.
Some 34 million people were living with HIV at the end of 2011, the report said. Deaths from AIDS fell to 1.7 million in 2011, down from a peak of 2.3 million in 2005 and from 1.8 million in 2010.
Worldwide, the number of people newly infected with HIV, which can be transmitted via blood and by semen during sex, is also falling. At 2.5 million, the number of new infections in 2011 was 20 percent lower than in 2001.
"Although AIDS remains one of the world's most serious health challenges, global solidarity in the AIDS response during the past decade continues to generate extraordinary health gains," the report said.
It said this was due to "historic success" in bringing HIV programmes to scale, combined with the emergence of new combination drugs to prevent people from becoming HIV infected and from dying from AIDS.
"The pace of progress is quickening - what used to take a decade is now being achieved in 24 months," said Michel Sidib?, executive director of UNAIDS. "We are scaling up faster and smarter than ever before. It is the proof that with political will and follow through we can reach our shared goals."
Since 1995, AIDS drug treatment - known as antiretroviral therapy - has saved 14 million life-years in poorer countries, including 9 million in sub-Saharan Africa, the report said.
Sub-Saharan Africa is the most severely affected region with almost one in every 20 adults infected, nearly 25 times the rate in Asia, there are also almost 5 million people with HIV in south, southeast and east Asia combined.
Some 8 million people were being treated with AIDS drugs by the end of 2011, a 20-fold increase since 2003. The United Nations has set a target to raise that to 15 million people by 2015.
"Scaling up HIV treatment to 15 million people ... is feasible and has the crucial triple benefit of reducing illness, reducing death, and reducing the risk of transmission," said Manica Balasegaram of the charity Medecins Sans Frontieres.
But he said the pace must be stepped up "so that every month more people are started on life-saving HIV treatment than the month before".
Scientific studies have shown that getting timely treatment to those with HIV can also cut the number of people who become newly infected with the virus.
UNAIDS said the sharpest declines in new HIV infections since 2001 were in the Caribbean and in sub-Saharan Africa - where new infections were down 25 percent in a decade.
Despite this, sub-Saharan Africa still accounted for 71 percent of people newly infected in 2011, underscoring the need to boost HIV prevention efforts in the region, UNAIDS said. Of the 1.7 million AIDS-related deaths in 2011, 1.2 million were in sub-Saharan Africa.
HIV trends are also a concern in other regions, it said.
Since 2001, the number of new HIV infections in the Middle East and North Africa was up more than 35 percent from 27,000 to 37,000, it said, and evidence suggests HIV infections in Eastern Europe and Central Asia began increasing in the late 2000s after being relatively stable for several years. (Editing by Alison Williams)