TPP ministers are due to resume talks in Singapore, following a week of demands for the New Zealand Government to release details of the proposed Pacific-trade agreement.
Trans Pacific Partnership (TPP) talks will begin on Saturday and run for four days, with ministers hoping to reach their target of an agreement by the end of the year.
New Zealand opposition parties voiced concern this week over the secrecy of the talks, which aim to set up free-trade agreement between 12 countries, including Australia, Japan and the US.
On Wednesday, five political parties fronted a press conference to demand disclosure of the proposed agreement, saying the government's secrecy is not matched by other TPP countries.
Opposition MPs are concerned America's intellectual property demands could impact on the ability of Pharmac, the government's drug buying agency.
They believe it could hinder the organisation's ability to deliver cheap generic drugs for New Zealanders.
The most recent talks, held in Salt Lake City, Utah, resolved "a substantial number of outstanding issues," the Office of the United States Trade Representative said.
"The work of the chief negotiators this week has significantly narrowed the number of issues to be addressed directly by the TPP ministers at their upcoming meeting in Singapore," a statement from the office said following the November talks.
The office said the parties hoped for a "productive meeting" among the TPP ministers in December.
The TPP negotiations began in 2007, aiming to expand the existing free trade agreement between Chile, New Zealand, Singapore and Brunei to include the US, Australia, Japan, Malaysia, Vietnam, Peru and Canada.