Secretary of State John Kerry on Tuesday hailed the 10th anniversary of a US program to battle AIDS, saying it has helped one million babies be born disease-free to mothers infected with HIV.

"Preventing mother to child transmission has been a central pillar of our fight against this disease," Kerry said at a State Department event.

More effective anti-retroviral drugs and regimens are now dramatically cutting the chances of an infected mother passing on the sickness to her baby during pregnancy or breastfeeding.

The birth of the one millionth HIV-free baby was hailed as part of celebrations to mark the 10th anniversary of the US President's Emergency Plan for AIDS Relief, known by its acronym PEPFAR.

"Thanks to the support of PEPFAR, we have saved the one millionth baby from becoming infected with HIV," Kerry said, adding it was "a truly landmark moment on the HIV/AIDS timeline."

"One million babies can grow up happy and healthy, go to school, realize their dreams, break out of this cycle, maybe even have sons and daughters of their own free from the burden and the fear of HIV."

Namibian Health Minister Richard Nehabi Kamwi said his government would always be "eternally grateful" for PEPFAR's assistance, which has helped turn the tide against the disease in his country.

The program "represents a decade of hope and renewed health for victims of HIV/AIDS, who without PEPFAR would have succumbed to the deadly pandemic," he said.

The biggest fall in transmission rates from mother to infant has come since 2009, US Global AIDS coordinator Eric Goosby told AFP.

"Somewhere round 430,000 babies are born annually with HIV and this project that we've been in really since the beginning of PEPFAR has intensified over the last three years in partnership with UNAID and UNICEF," Goosby said.

The program was working to "virtually eliminate pediatric HIV by 2015 and keep their mothers alive," he said, with the aim of reducing the number of babies born with the infection to around 30,000 annually.

This involves not just identifying the mother, but getting her on a drugs program and keeping her in treatment through the pregnancy and any later ones -- not always an easy task in rural Africa.

The chances of a mother infecting her baby once stood at around 30 percent, but now, with the launch of a cocktail of three anti-retroviral drugs, that has dropped to only about two percent, Goosby said.

Launched under former US president George W. Bush, PEPFAR was an initial commitment of some $15 billion over five years aimed specifically at providing anti-retroviral drugs to people infected with HIV.

That has risen to a budget of about $5.5 billion annually, including its contribution to the Global Fund -- the world's largest financing organization of programs to fight AIDS, tuberculosis and malaria.

Kerry told how during a visit some years ago to Durban, South Africa, he had met orphans robbed of their parents "forced to take on the burden of adulthood at the age of 13, 14, and caring for their younger siblings."

"We were heartbroken in hearing what these children had been through. You couldn't help but feel this agony and this total disruption of the way life is supposed to be."

But with programs like PEPFAR, "when we all looked lost, when this disease appeared to be unstoppable, history will show that humanity and individual humans rose to the challenge."

"Action was taken, innovations were discovered, hope was kindled and generations were saved," Kerry said.

Absent a medical breakthrough leading to a cure, experts are working towards a so-called "tipping point" when fewer people contract HIV every year than the number of those going onto treatments.

Kerry also announced that some 13 countries from Botswana to Zimbabwe, including Namibia, were close to that all important "tipping point."

In Ethiopia and Malawi, the ratio of new HIV infections to the increase of patients on treatment is just 0.3. Ethiopia -- which with a population of 84.7 million is the most populous African country after Egypt -- for instance registered only 11,000 new cases of HIV in adults in 2011.

Although some 1.7 million people still die every year from AIDS-related illnesses, PEPFAR supports more than 5.1 million on treatment programs.

The program estimates that worldwide more than 16 million children are living without one or both parents who have succumbed to AIDS, while millions more are left vulnerable with their parents chronically ill.