Associate Health Minister Tariana Turia says she feels the United States is putting pressure on New Zealand regarding the plain-packaging of tobacco.
The Government on Monday began consultations on whether branding should be removed from tobacco packets.
Prime Minister John Key denies that plain-packaging has ever been flagged as a point of contention in the Trans-Pacific Partnership trade talks.
But Mrs Turia says she suspects the US is putting pressure on.
"It is my feeling because there have been companies in the United States that have come out supporting the tobacco companies and one of the tobacco companies, of course, is from the US, so obviously there is a link there."
However she said, in the end, New Zealand determines its own regulations.
Should tobacco companies try to fight plain-packaging, official estimates put a cost of up to $6 million on defending an international investment arbitration case.
Mr Key says signing the TPP trade deal would not affect New Zealand's sovereignty over something like plain-packaging.