The deal would see rules on drug patents relaxed
The World Trade Organisation's executive has delayed final approval of a deal to give some of the world's poorest countries access to cheap drugs.
The 146 WTO members had earlier agreed in principle to a deal that could see millions of people around the world receiving medicines to treat killer diseases for the first time.
The executive had been expected to rubber stamp the deal late on Thursday, but the decision was delayed following a last-minute hitch.
It is understood that the delay has been caused by up to two dozen countries who are unhappy about the wording of a 'chairman's statement' agreed by the US, Brazil, India, Kenya and South Africa.
The five had previously been at loggerheads over plans to make cheap medicines more widely available.
WTO spokesman Keith Rockwell said: "There is no deal. More consultations are required."
The principle of allowing developing countries access to cheap versions of key drugs had been agreed at WTO talks almost two years ago but talks had dragged since then on implementing the deal.
Many of the drugs at issue are patented, which means they cannot be copied for 20 years. The WTO talks aimed to ease these rules for some medicines, enabling countries in need to import cheaper versions of essential drugs.
Last December, the United States had blocked a deal on cheap drugs - even though it was backed by all other members of the WTO.
US negotiators said it would allow too many drugs patents to be ignored.
They said the proposed deal would mean that illnesses that are not infectious, such as diabetes and asthma, could also be treated with cheap, generic drugs.
But it was understood that the US would lift its opposition to a deal if WTO states pledged not to abuse the system and to only waive patents "in good faith" and not for commercial gain.
They would also be expected to take all reasonable steps to ensure cheap versions of drugs do not make their way onto markets in rich countries.
South Africa's top trade envoy Faizel Ismail had described the plan
as "reasonably balanced" and "close to an acceptable solution".
"It provides some comfort to the US pharmaceutical
companies that were worried about abuse," he said.
The issue has been casting a long shadow over global free trade talks since their launch in 2001.