Negotiators from the United States and 10 other countries are holding closed-door talks in Singapore from March 4-13 on the proposed Trans-Pacific Partnership (TPP) as they race to seal an accord.
"It's getting tougher and more challenging towards the end. There might be some problems in meeting that deadline, October 2013," Malaysian Trade Minister Mustapa Mohamed told the Foreign Correspondents Association of Singapore after the talks opened.
Activists pushing for greater public access to cheap generics are sparring with the pharmaceuticals industry, which was worth $355 billion in 2010 among the 11 countries involved in the talks, with US firms accounting for 80 percent of the market.
The dispute illustrates the complexity of the TPP, which has already missed a 2012 deadline due to differences over non-tariff issues like labour standards, environment protection, government procurement and intellectual property rights.
Some countries are also keen to impose protection for sensitive sectors like agriculture and cars.
On pharmaceuticals, humanitarian group Medicins Sans Frontieres (Doctors Without Borders) asked negotiators from developing countries to reject what it claimed are patent provisions being pushed by Washington restricting access to generic drugs.
MSF cited what it said was a leaked draft of the US negotiating position threatening to keep "monopoly protections that keep medicine prices high".
It warned that if other countries in the Asia-Pacific region eventually opt into the TPP, tighter patent protection may make new medicines out of reach to a wider number of people.
US President Barack Obama has mooted the TPP as a centrepiece of renewed American engagement in Asia.
The talks currently involve Australia, Brunei, Canada, Chile, Malaysia, Mexico, New Zealand, Peru, Singapore and Vietnam.
Japan has said it wants to join the process, but is expected to face strong domestic opposition against opening up its farm sector.
China is not involved in the talks, preferring to concentrate on other Asian trade pacts that analysts say require less stringent commitments.
MSF said one provision advocated by US negotiators in the TPP is the grant of new 20-year patents for modifications of existing medicines, making it harder to make cheaper generic versions.
Another provision makes it "more expensive and cumbersome to challenge" invalid patents, while another would add more years to a patent term to compensate for administrative processes, MSF added.
Pharmaceutical companies argue that copyright protections are necessary to allow them to recover investments and continue research on new cures.
The Pharmaceutical Research and Manufacturers of America (PhRMA), which sent representatives to monitor the Singapore talks, urged negotiators to adopt robust intellectual property (IP) protections.
"A weak IP framework within TPP would create uncertainty at a time when we need to be doing more to champion researchers and innovators who rely on strong protections," said Jay Taylor, PhRMA vice president of international affairs.
Taylor told AFP that PhRMA wants a provision that will give companies 12 years of data protection on new "biologic" medicines, which are made with living tissues in contrast to drugs made by compounding chemicals.
They are already being used to treat cancer and diabetes and are crucial in developing new cures, he said.
The 12-year protection should start from the time the new medicine is approved by regulators for release into the market, he said.
Taylor added that it takes an average of 10-13 years and more than $1.0 billion in investments to develop a new cure, but not all research projects are successful and some could lead to financial losses.
Medicine patents currently last 20 years, but Taylor said that research and development eat up more than half of the period as the coverage starts from the time the molecule is identified.