Prime Minister John Key says New Zealand could live with some extension to drug patents, but not a dramatic one, in a Trans-Pacific Partnership free trade agreement.
The talks in Atlanta remain bogged down after two days of negotiations between ministers from the United States, Australia, Japan and nine other countries over a handful of sticky issues.
A US push to establish longer patent protections for biologic drugs - those made using living organisms - remains unresolved, AFP reports.
"We could live with some extension, but not, we don't think a dramatic one," Mr Key told TV3's The Nation.
"Everything I've seen so far allows me to continue to say I think that we are progressing towards something that would absolutely be in New Zealand's best interests.
"If it's not, New Zealand won't sign it," he said.
"But we are in that crunch point with dairy where we need to get more for New Zealanders if we can and that's what we're working on," he said.
A deal is within reach as negotiations in Atlanta are at crunch point, Trade Minister Tim Groser said yesterday.
"It's within reach but I can't touch it yet," he said.
But he conceded that how the negotiations would turn out was anyone's guess.
Professor Jane Kelsey, an opponent, says for New Zealand "the dead rat seems to be a dairy for medicines deal".
"If this happens, we can expect the minister to hail the 'net benefits' of the TPPA to New Zealand, playing up supposed gains to dairy exports that remain to be seen, she said.
Any deal on biologic drugs would be played down, she said.