As Donald Trump virtually locked up the Republican presidential nomination, nations in Asia began to more seriously assess the potential global impact of a Trump administration.
“We never imagined this would happen,” said a senior Japanese Foreign Ministry official. The ministry’s staff recently began compiling Mr. Trump’s past statements about Asia and analyzing what effect a Trump presidency would have on the region. But the task has been slow-going, the official said. “Too much about Mr. Trump’s position and the positions of his advisers is unknown.”
The presumptive Republican nominee has accused some allies of being free riders and warned of a rebalancing of financial commitments, sparking particular concern in a region where China has become more assertive militarily and North Korea has recently carried out atomic bomb tests and missile launches.
Yuichi Hosoya, a member of Prime Minister Abe’s security advisory panel and a Keio University professor, said a Trump presidency could benefit China’s geopolitical ambitions in Asia. “China wants the U.S. to pull away from the region as much as possible to create a regional order that maximize China’s profit and security,” Mr. Hosoya said.
Mr. Trump has been a strong critic of China’s trade policies, which has had a sobering effect on some observers in the country. Shi Yinhong, an international-relations expert at Beijing’s Renmin University, said he was wary of Mr. Trump’s antitrade stance.
“Based on what he’s said so far, if he were to become president, I’m afraid U.S.-China relations would suffer some major upheaval,” Mr. Shi said.
A spokesman for China’s Ministry of Foreign Affairs declined to comment on Mr. Trump’s status as the presumptive GOP nominee at a regular press briefing on Wednesday, saying it was “an internal affair of the U.S.”
In South Korea, Mr. Trump has created some anxiety by saying that Seoul unfairly benefits from the protection of the U.S. military, which has around 28,500 troops in the country and is obliged by a bilateral treaty to provide defense from any North Korean attack.
A senior official at South Korea’s Foreign Ministry said Seoul was seeking to contact the campaigns of the U.S. presidential candidates, including Mr. Trump’s, to explain the Asian nation’s foreign policy and ensure smooth communication.
On Wednesday, the national daily JoongAng Ilbo said in an editorial that South Korea needs to prepare for a possible withdrawal of U.S. forces and warned that Mr. Trump’s vow to impose tariffs on Chinese products could start a trade war.
Mr. Trump has said that the U.S. should end military arrangements with countries such as Japan and South Korea and allow them to build their own nuclear arsenals.
Tang Siew Mun, who heads the Asean Studies Centre at the ISEAS Yusof Ishak Institute in Singapore expressed concerns about the fate of the pending Trans-Pacific Partnership trade deal under a Trump administration. “Japan, Vietnam and Malaysia have expended enormous domestic political capital to get on board the TPP and a U.S. back down will have serious ramifications for their bilateral relations with the U.S.,” Mr. Tang said.
In Australia, political reaction over Mr. Trump’s ascendancy has been muted, with Prime Minister Malcolm Turnbull having several times declined to comment on the Republican race and Mr. Trump’s ascendancy to avoid diplomatic ructions with Canberra’s main strategic ally.
“That is a matter for the American people,” Mr. Turnbull said last month when asked if he could ever see himself lining up with Mr. Trump at an international summit.
But Michael Fullilove, who heads the Lowy Institute, a Sydney-based international-affairs think tank, said Mr. Trump’s victory in Indiana Tuesday night was a “bracing day for America’s friends in Asia.”
Ted Cruz’s withdrawal from the presidential race “means that the Republican Party—traditionally strong on Asia—will be led by a man who is wholly allergic to America’s alliance network.”
Mr. Trump does have his supporters in Asia. At the new Trump Tower Manila, a 56-story development due for completion later this year, Filipino builders and security guards working on the site expressed strong support for Mr. Trump’s presidential bid Wednesday, though they said they knew nothing of his tussle with Mr. Cruz. “Definitely, if he wins it will be good for the Philippines,” said overseer Jerry Garcia. “We all like him. His sons have visited us here.”
—Alastair Gale, Yuka Koshino, Trefor Moss and Celine Fernandez contributed to this article.
Write to Mayumi Negishi at firstname.lastname@example.org, Josh Chin at email@example.com and Rob Taylor at firstname.lastname@example.org