Dairy co-operative Fonterra says it remains unclear how much access the United States will offer to its protected dairy markets in free trade talks.
US farmers strongly object to access being given as part of the discussions on a TransPacific Partnership (TPP).
Fonterra can only sell 22,000 tonnes of cheese to the US before having to pay high tariffs. The US market takes 4.5 million tonnes of cheese.
The dairy company wants the tariffs scrapped but says it is not clear how much US negotiators will heed American farmers' demands in the current TPP negotiations.