Prime Minister John Key has arrived in Washington for two days of top level talks culminating in a meeting with President Barack Obama.
Mr Key has put the Trans Pacific Partnership at the top of his agenda.
The Trans Pacific Partnership has broad support from the American business sector, with the United States Chamber of Commerce saying securing a deal is important, and would help create jobs at a time of high unemployment.
But the US Dairy Export Council is pushing to have New Zealand dairy exports excluded from any deal, saying Fonterra is a virtual state monopoly and enjoys advantages its competitors can not match.
Council president Tom Suber says as long as the dairy co-operative stays that way, it is not in the US interest to open its market up further.
Mr Suber says the US dairy industry has substantial support for its position within Congress, which would ultimately have to sign off on any trade deal.
The American consumers rights group, Public Citizen, agrees, saying the dairy industry lobby is strong in the US, and is likely to get its way.
Public Citizen also opposes the Trans Pacific Partnership, which it says is more about new rights for multi-nationals than it is about trade.
Its global trade watch director Lori Wallach says the partnership trade talks will give foreign corporations extensive new rights but New Zealand is unlikely to get much in terms of trade access.
She says the proposed deal would affect government's ability to introduce new environmental, financial and public health regulations.
