Differences have emerged between Prime Minister John Key and Trade Minister Tim Groser over Japan's entry into the Transpacific Partnership free trade agreement (TPP).
Japan's cabinet announced over the weekend that it would begin preparatory discussions for inclusion in the TPP - prompting immediate opposition from the country's powerful farming lobby.
Mr Key says the TPP countries, including New Zealand, should not lower the bar for Japan's inclusion in the talks but Mr Groser says more flexibility is needed.
John Key says the nine TPP countries have so far agreed to hold to the terms under which new members should be accepted, and that no exception should be made for Japan.
But Tim Groser, a former top official at the World Trade Organisation, says that's not realistic.
"Countries that have difficulties in liberalising agriculture have difficulties for reasons - it's not cussedness on their part.
"So therefore a politically experienced negotiator would never just say 'take it or leave it'. No, no it'll have to be much more subtle than that."
Tim Groser says Japan could be allowed a lengthy period before it lowers its tariffs on agricultural imports, if that makes it easier to win political acceptance for the deal at home.