Officials from 12 countries including the US, Japan and Australia appear close to a deal on an ambitious Pacific Rim trade pact, with negotiations heading into the second day of overtime.
Late on Friday officials said an agreement on the Trans-Pacific Partnership was within reach, though it was not clear if the final grudging issues of protections for certain drug patents, and lowered trade barriers on auto parts and dairy products, were fully resolved.
Pressure was intense on negotiators on Saturday, especially those from Australia, Canada, Japan, New Zealand and the United States, not to undercut important home industries as they bargain over the remaining unresolved points of the broad-ranging treaty.
The auto and dairy trade issues were still apparently on the table late on Friday.
But the main barrier to a final deal was the length of intellectual property (IP) protection for biologics, a promising class of treatments derived from living materials.
The United States is seeking longer protections than the five years common in many countries.
In the United States, pharmaceutical companies get 12 years of IP protection before rivals can produce "biosimilar" copycat drugs that sell more cheaply. But in most countries, the US protections for drug developers are seen as far too long, and costly, for health care systems.
The issue has raised objections from civil society groups and government health programs across many of the countries involved in the negotiations.
Rather than a problem of just cutting tariffs or other trade barriers, lengthening protections could in many places require changing well-established national laws and IP protection policies.
According to one source informed on the progress of the talks, strong resistance to Washington's stance was coming from Australia, Chile and Peru.
The talks between top trade officials in Atlanta have gone well past the original Thursday deadline.
A number of trade ministers in the group had their eyes on their travel schedule: the G-20 group of leading economies is holding a meeting of trade ministers on Monday and Tuesday in Istanbul.
The arrival of officials from the US Congress at the hotel venue for the TPP talks on Friday also suggested that an agreement was in the air.