US President Donald Trump will offer a clearer picture on why he and other senior White House officials have begun referring to the Asia-Pacific as the “Indo-Pacific” by the end of his 12-day, five-nation tour of the region, Washington’s envoy in Tokyo said on Tuesday.

Trump had discussed the Indo-Pacific “concept” with Prime Minister Shinzo Abe, ambassador William Hagerty said following the president’s two-day Japan visit, adding it was too early to draw conclusions on the reasons behind its use.

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The use of the term was a departure from language employed by previous administrations, and has led to speculation that it could have to do with Washington softening the ground for a revival of the so-called Quadrilateral strategic alliance consisting of the US, Japan, Australia and India to counter China’s rise.

The four democracies have not formally convened as a group for a decade, and the bloc is viewed by Beijing with a degree of suspicion.

US and Japanese officials have said a comeback may be on the cards for the grouping.

A Chinese foreign ministry spokesman responded by cautioning that the alliance should not target a “third party”.

“When we talked about the Indo-Pacific region, when the prime minister and President Trump talked about that, we mentioned a number of countries that are involved in that region but we did not mention them in the specific quadrilateral structure or framework,” Hagerty said in a phone interview debriefing regional journalists about Trump’s visit.

“Right now the president is here to listen, have conversations and talk about this concept and I think that will further clarify itself as he goes all the way through to the [Apec] conference in Vietnam,” Hagerty said, referring to the Asia-Pacific Economic Cooperation forum. “I would expect more definition around that at the end of this trip.”

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National Security Adviser H R McMaster last week repeatedly used the term in a press briefing on Trump’s Asia tour, which will take in the Philippines, Vietnam, China and South Korea alongside Japan. Trump was in Seoul for a day-long stopover on Tuesday.

The US commander-in-chief also used the term in public remarks before a cabinet meeting last week.

And a fortnight ago, US Secretary of State Rex Tillerson used the term “Indo-Pacific” some 15 times in a speech detailing how Washington’s democratic allies like Japan and Australia should work together to counter what he termed China’s challenge to the “rules-based international order”.

Hagerty sidestepped questions on the South China Sea territorial dispute between China and Southeast Asian nations.

Instead, the US envoy said the “primary point of discussion” between Abe and Trump was on North Korea. “The South China Sea is always an area of interest to us … but I will have to say that the headlines certainly have been dominated by the situation in North Korea,” Hagerty said.

The ambassador said both leaders were “very determined to put the maximum amount of economic and political pressure on the [North Korean] regime to achieve the denuclearisation” of the Korean peninsula.

Asked about the prospects of the 11 remaining nations in the Trans-Pacific Partnership (TPP) trade pact conferring at the sidelines of this weekend’s summit of Asia-Pacific leaders in Danang, Vietnam, Hagerty said the US saw no conflict between a deal being struck and its own efforts to seal bilateral free-trade deals with countries in the region.

The original 12-nation TPP was derailed in January after Trump withdrew the US from the pact soon after he was sworn in, keeping with a campaign pledge to end a deal he said would take away US jobs.

That laid waste to nearly eight years of negotiations done over 32 rounds – a process prolonged by the Barack Obama administration’s expectation for a high-quality deal.

The US accounted for 60 per cent of the group’s total gross domestic product in the original pact, but the remaining 11 countries have pressed on with negotiations for a more modest deal. Along with the US, they had collectively reached an agreement on terms in October 2015.

“The momentum towards [an agreement] at the meeting in Danang has significantly increased,” Japan’s chief TPP negotiator Kazuyoshi Umemoto said last week.

The “TPP 11” countries are: Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Vietnam and Singapore. They have a combined GDP of US$12.4 trillion.