The party's support is suddenly pivotal to the success of the rebranded 11- country trade partnership.
Trade ministers from 11 Pacific Rim countries have announced an agreement on pushing ahead with a free-trade deal whose destiny was uncertain after President Donald Trump dropped it.
The talks resulted in a rebadging of the trade pact to the Comprehensive and Progressive Agreement for Trans-Pacific Partnership. The ministers also said they would work to improve the functioning of the World Trade Organisation (WTO) - which Trump criticized in Friday's speech.
That involved a hard balance between maintaining high standards and pragmatism, Mr Motegi said.
"We are not going to let the United States be taken advantage of anymore", Trump told business leaders at the Asia-Pacific Economic Cooperation forum in Danang, Vietnam.
The announcement of a basic agreement was delayed by last-minute discord that prevented the TPP leaders from endorsing the plan when Canadian Prime Minister Justin Trudeau did not join other leaders to endorse an agreement in principle on pressing ahead without the US. China is not part of the TPP.
Over the last few months, Japan and Australia had lobbied hard for the agreement.
Partly to counter China's growing dominance in Asia, Japan had been lobbying hard for the TPP pact, which aims to eliminate tariffs on industrial and farm products across the 11-nation bloc whose trade totalled $356 billion previous year.
After Trump abandoned the agreement two days after being sworn into the presidency, the pact appeared moribund, but the leaders managed to rescue the pact on Saturday.
New Zealand had made good progress on contentious investor-state disputes resolution clauses and preserving market access, she said. Canada's trade minister later blamed Trudeau's absence on "a misunderstanding about the schedule".
It's understood Canada, the second largest economy in the TPP since the United States withdrew, had been in bilateral talks with Japan on role difference before Trudeau's no show at the meeting. Trump has said he prefers country-to-country deals and is seeking to renegotiate several major trade agreements to, as he says, "put America first".
Meanwhile, the statement issued on Saturday said a "limited set of provisions" from the original deal would be suspended, adding further technical work was needed on four areas that still needed consensus "to prepare finalised text for signature".
The deal would be the largest trade agreement in history even without the US, and it would allow for tariff-free trade between members, boost intellectual property protections and open markets to free trade.
The American President added that the USA would no longer "enter into large agreements that tie our hands" but focus on country-to-country agreements.