Prime Minister Jacinda Ardern is on her way to Vietnam where she'll seek to renegotiate parts of the Trans-Pacific Partnership.
Ms Ardern will be attending but not co-hosting a meeting with Japanese Prime Minister Shinzo Abe where leaders of the remaining 11 partner nations will be looking to finalise an agreement.
The New Zealand government is expected to push hard for renegotiation of investor-state dispute settlement clauses which allow foreign investors to sue governments.
But there's fears from Japanese officials, who have been leading negotiations since the US withdrawal earlier this year, that renegotiations could collapse the agreement.
Opposition leader Bill English is urging Ms Ardern to "pull out all the stops" to complete the TPP and says she can count on National's support.
"Officials and ministers have done the hard work, it's time to finish the job," he said.
"It is a high-quality trade deal that will have real benefits for all 11 countries."
Ms Ardern's time in Da Nang will also include a speech to a women's forum, breakfast with New Zealand business leaders and a speech at the APEC CEO's forum.
Almost a dozen bilateral meetings are also on the agenda in Vietnam and Manila, in the Philippines where Ms Ardern will later be attending the East Asia Summit.
Canadian Prime Minister Justin Trudeau is expected to be among the leaders Ms Ardern meets with.
Deputy Prime Minister Winston Peters will join Ms Ardern for both summits.
Trade Minister David Parker will attend TPP talks in Vietnam and his associate minister Damien O'Connor will travel to the Philippines.