Trade Minister Tim Groser says the United States is digging its heels in over a crucial aspect of the TransPacific Partnership free trade talks, (TPP).
Eight countries, including New Zealand, have completed two rounds of negoations and held further talks late last month in Peru.
At the conference in Peru, the US stuck to its preference to negotiate afresh with countries it does not have free trade deals and leave existing deals in place.
Mr Groser says that scenario is dangerous to New Zealand's goal of getting better access than Australia achieved in its deal with the US in 2003.
Australia joined the TransPacific Partnership in 2008 to improve on what was considered a low-quality deal with the United States in sectors like sugar and dairy.
While it's possible in theory to get better access than Australia in the TPP under the preferred scenario of the United States, Mr Groser says politically it's unlikely.
Malaysia and Canada also attended the talks in Peru with a view to joining TPP.
Prime Minister John Key in April expressed concerns about Canada joining the TPP because of its heavily subsidised dairy industry.
Mr Groser says those concerns have not been addressed by Canada, but Malaysia is close to joining.