The Cabinet has formally approved a negotiating mandate for the TPP 11 - the Trans Pacific Partnership without the United States - but one that would involve minimal renegotiation.
New Zealand has also been asked to co-chair a meeting of TPP countries with Japan in November in Vietnam on the sidelines of Apec.
But if Labour and New Zealand First form the next Government after the September 23 election, New Zealand will be withdrawing from the TPP, and not taking a leadership role in keeping it alive.
Jacinda Ardern would not likely be co-chairing a TPP meeting with Japan's Prime Minister Shinzo Abe in Vietnam.
The TPP effectively gives New Zealand a free trade agreement with Japan, the world's third-largest economy, Canada, Mexico and Peru. The US has been withdrawn from the deal by President Donald Trump.
Trade Minister Todd McClay said today that New Zealand would be pushing for the minimal number of changes, which had been agreed on by the 11 remaining countries.
Minimal change means altering the trigger by which it enters into force.
Officials met in Japan last month and will meet in Australia next month to prepare the proposal to put to leaders in November.
McClay said it was imperative that New Zealand continued to show leadership on TPP to remain competitive.
Japan had just concluded a free trade agreement with the European Union which gave better access to European exporters than New Zealand currently had.
"Japan has also just announced it will a apply a 50 per cent tariff on all frozen beef import from countries it doesn't have an FTA with."
But the TPP would reduce tariffs on New Zealand beef exports from 50 per cent to 9 per cent.
Prime Minister Bill English told reporters he was optimistic that TPP11 would get the green light in November.
"Having Japan in there, as the third-biggest economy [in the world] is a pretty important part of taking it forward without unstitching the original agreement," he told reporters in Wellington.
"Six months ago, no one thought TPP 11 could happen but we've got this far. It has exceeded expectations.
"Given the determination we see among countries to almost prove a point about free trade, we are optimistic we can get there."
Winston Peters, the leader of New Zealand First, which along with Labour and the Greens opposes TPP, criticised the Government for going ahead with the deal despite the withdrawal of the United States, without consulting the New Zealand Parliament or people.
"This is government by tyranny and not for or on behalf of the people. Secrecy, scheming and arrogance are not what New Zealanders want."
The TPP11 are New Zealand, Australia, Japan, Malaysia, Singapore, Brunei, Vietnam, Peru, Chile, Mexico and Canada.