Developing countries want the rules relaxed to allow them to import or manufacture cheap generic versions of patented drugs.

Historically the US has been a staunch supporter of the current laws, arguing that companies need to be assured of the money from patents to plough into research.

But anthrax scares in the US seem to have weakened the government's stance and earlier this week it threatened to override the patent held by German drugs company Bayer on anti-anthrax drug, Cipro, if the company didn't agree to a substantial price cut.

After negotiations Bayer agreed to slash the price of Cipro to below $1 per tablet.

Ambiguous rules

The disputes over reproducing patented drugs on the cheap arise from ambiguous clauses in WTO rules on intellectual property.

According to the WTO's Trade-Related Aspects of Intellectual Property Rights (TRIPS), member countries are required to recognise international patents on medicine.

However, the rules also say that "this requirement may be waived by a member in the case of a national emergency or other circumstances of extreme urgency".

However, as a WTO spokesman points out, "there are no clear boundaries defining an emergency and this has not been tested in the courts".

Adrian Lovett, policy and campaign coordinator at the development charity Oxfam, told the BBC's World Business Report that the WTO needs to make clear that "the health of people in national emergencies is more important than the profits of private companies."

Bimal Raizada, Senior Vice President of Indian drug company Ranbaxy, said he believed that generally pharmaceutical companies were responsive if approached by governments facing national health emergencies.

Government u-turn

Just last summer, the US was planning to file a complaint with the WTO against Brazil for allowing the alternative production of patented Aids-treatment drugs.

In June it dropped the complaint, announcing that it preferred "to resolve trade disputes by seeking constructive solutions".

US protectionism with regard to its domestic pharmaceuticals industry was also evident in a long-running dispute with South Africa.