Labour Party delegates are due to decide at their annual conference in Christchurch whether the party should take a more cautious approach to the Trans-Pacific Partnership negotiations.
Under a union-sponsored amendment, Labour is likely to agree it should withhold support for the agreement unless it benefits the country and does not compromise its sovereignty.
Labour Party leader David Cunliffe says the proposal does not mean Labour opposes the deal.
Mr Cunliffe says the party is very aware of the potential benefits of a trans-Pacific trade agreeement, which includes the United States.
However, he says there are genuine concerns about its possible impact on this country's domestic regulations and on drug buying agency Pharmac.
Mr Cunliffe says the Government should make more information about the negotiations public so New Zealanders can decide whether the proposed deal is a good one or not.
