"That is the absolutely central concern that I have," he told the Herald from Sydney airport last night after spending the weekend at a TPP ministerial meeting.
"The US interests are not New Zealand's interests."
He had spoken to both his Japanese and American counterparts, Akira Amari and Mike Froman, to implore them not to finalise a deal that would simply be imposed on New Zealand.
"I said New Zealand is the largest dairy exporter in the world so you can't just brush us aside.
"We have standing in this argument."
Mr Groser accepted that the outer parameters would be settled by Japan and the US, but it should not be finalised without New Zealand.
"We've said, 'Don't do the deal. Outline generally where you want to go, but do not just close this deal and try and impose it because that will cause a timebomb in this negotiation'.
"They know that if they try to make a sweetheart deal that benefits just them and not Australia and New Zealand, it is going to cause massive political problems in getting us on board."
Besides that, Mr Groser said it was the best TPP ministerial meeting he had attended.
The part of the negotiations about trade rules such as intellectual property were going very well and he and the New Zealand negotiators were more confident about getting "a perfectly reasonable result".
"I think the finish line for TPP is in sight -- but that does not mean we are going to successfully cross it," he said.
If it did succeed, it would come together in the first quarter or first half of next year.
The countries negotiating the TPP are Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, the United States and Vietnam.
By Audrey Young of the New Zealand Herald