Labour may have to pass the CPTPP into law with the support of National and ACT - and without its Government support partners.
Prime Minister Jacinda Ardern says New Zealand First won't make a decision on whether it backs the CPTPP (the rebranded Trans Pacific Partnership Agreement) through Parliament, until it's seen the final deal.
Labour already knows it doesn't have backing from the Greens.
Earlier on Monday, the Greens reiterated its decision to vote against the deal, while investor-state dispute settlement mechanisms remained an option.
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Without support from either Government partner, the CPTPP can still easily pass through into law. National says it does - and will - support the agreement.
Speaking from the Philippines, Ms Ardern said, despite New Zealand First having Cabinet responsibility, it also had the ability to agree to disagree.
"We won't have a conversation about where party support will fall, until we have a final agreement," she said. "I absolutely understand parties in some cases will wait until the final deal's on the table."
From time to time, Labour, New Zealand First and the Greens will take differing positions, she said.
Ms Ardern has had ongoing conversations about the deal with NZ First leader Winston Peters.
The TPP agreement initially included the United States, but President Donald Trump withdrew from the agreement, forcing the remaining countries to form a TPP11 agreement.