About 1,800 babies are born with HIV each day because their mothers do not get the drugs they need, the World Health Organization has warned.
Drugs prevent babies being infected with during childbirth
Under 10% of pregnant women with HIV in developing countries received antiretroviral drugs between 2003 and 2005, a report by the WHO said.
It also revealed a total of 1.3 million now get the drugs, short of the target of 3 million set by the WHO and UNAids.
The new goal is for universal access to treatment by 2010.
The report, released with UNAids, said that although the 'Three by Five' target had not been met, important lessons had been learnt.
And it said 18 countries had met the target to provide treatment to at least half of those in need.
The report found access has improved across the world since the WHO and UNAids launched their initiative in December 2003 to get three million people onto antiretroviral therapies by 2005.
About 50,000 people started taking the treatment each month in the past year, the report said, estimating that 250,000 to 350,000 premature deaths have been averted in developing countries as a result of expanded treatment access.
The amount spent on HIV/Aids across the world rose from $4.7 billion in 2003 to $8.3 billion in 2005, with much of the funding coming from the US President's Emergency Plan for Aids Relief, the Global Fund to Fight Aids, TB and Malaria, and the World Bank.
During the same period, the price of first-line treatment decreased by between 37 % and 53%, depending on the drug regimen used, the report said.
The report said the failure to make better progress towards the Three by Five target was due to ineffective partnerships among aid providers, inadequate supplies of drugs and weak health systems, the report said.
It also said 660,000 children under the age of 15 were in immediate need of antiretroviral therapy in 2005.
Most live in sub-Saharan Africa, the region hardest hit by HIV and Aids. Only 17% of patients there had access to the life-saving drugs last year.
The Group of Eight rich nations pledged in July 2005 to work with WHO and UNAids to move as close as possible to universal treatment access by 2010.
The report said that goal ought to be attainable, but warned substantially more funds would be needed to achieve it.
UNAids said there was an $18 billion gap for the 2005 - 2007 period between available and needed resources.
By 2008, it said at least $22 billion per year will be needed to fund national HIV prevention, treatment and care programmes.
Peter Piot, executive director of UNAids, added: "Misinformation about the disease and stigma against living with HIV still hamper prevention, care and treatment efforts everywhere.
"If we are to get ahead of the Aids epidemic, we must tackle stigma, ensure that the available funds are spent effectively to scale up HIV prevention, care and treatment programmes and mobilise more resources.
But the organisation Medicin sans Frontieres warned that without a concerted effort by the UN and the international community to make sure there is a steady supply of low-cost AIDS drugs, attaining the goal of universal access would remain impossible.