Prime Minister Jacinda Ardern leaves for Apec in Vietnam this morning secure in the knowledge that National will support any TPP deal finalised there.

Former Trade Minister Todd McClay pledged in Parliament last night that the new Labour-led Government could count on National's support.

He said given that because New Zealand First and the Greens had not supported any trade deals, he wanted the Government to know it could go into the crucial talks secure in the knowledge it would be able to meet its commitments.

"The Government and our negotiators will be able to go overseas knowing that they have the support of this Parliament and when they come back with a high quality deal, New Zealand can honour its commitments," he said.

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"They can go and deal the best deal possible."

National and Labour votes combined make up 102 of the 120-seat Parliament.

The TPP has already been ratified and legislation has already been passed, but it related to a deal involving 12 countries, including the United States, which President Donald Trump has withdrawn from.

New legislation would be required to give effect to the deal to TPP11 now being negotiated on the sidelines of Apec.

New Trade Minister David Parker and Foreign Minister Winston Peters are in Danang already for ministerial meetings.

Ardern and the other 10 leaders are due to meet tomorrow evening, NZ time, to determine the deal's fate.

New Zealand is trying to get other countries to agree to drop the Investor-State Dispute Settlement provision in the agreement but they are not likely to get every country to agree.

However Ardern has hinted that lack of agreement from all of them would not be a deal-breaker.

Labour deputy leader Kelvin Davis will be Acting Prime Minister while Ardern and deputy PM Peters are away.

Davis will be answering questions on Ardern's behalf in Parliament today during the first Question Time of the new Parliament.