He has also threatened to rein in China’s big trade surplus with the US, saying he will threaten to impose heavy duties on Chinese goods. And Trump says he will rip up and then renegotiate the Trans-Pacific Partnership, a trade pact agreed to by the US, Japan, and 10 other countries in February.

Furthermore, Trump’s call for a ban on Muslims entering the United States risks undermining moderate leaders in Muslim countries like Pakistan, Indonesia, Malaysia and Bangladesh.

“If he becomes president and adopts his own version of foreign policy, the US will cease to be a Pacific power. That’s the end result,” said Kunihiko Miyake, a former Japanese diplomat, who served in both Beijing and Baghdad.

“It’s not that we would adopt ‘Japan First’, but if the US leaves, there will be a vacuum and China will try to fill it,” said Miyake, research director at the Canon Institute for Global Studies. “It’s a survival issue for all allies of the United States.”

Trump could, of course, lose the election to the likely Democratic candidate, Hillary Clinton, who is well known by many Asia policymakers. And if he is elected he could act a lot differently in office. But Asian diplomats and policy advisers say that initial impressions count.

His idea of making Japan and South Korea pay up rather than enjoy a cheaper ride under the US security umbrella sent shudders through Tokyo and Seoul.

And his comments about the possibility of a local nuclear deterrent fanned fears among Asian diplomats that the world could become an even more dangerous place.

“It is here that Trump is most scary,” Lalit Mansingh, a former Indian ambassador to Washington, said in New Delhi, though he also noted it may be “just election rhetoric”.

Japan’s nationalist-led government has already boosted defence spending and has reinterpreted its pacifist constitution to allow its military to come to the aid of allies under attack even if Japan itself if not attacked, a major shift in Japan’s post-war security stance.

“His position is causing anxiety, especially in East Asia,” said a senior lawmaker in Japan’s ruling coalition. “It is really hard to comprehend because conservatives have supported a stronger military presence and more engagement.”

Mansingh said he expects China to test the foreign policy resolve of whoever occupies the White House next, and the South China Sea looms as one of the most likely flashpoints.

Tensions over China’s land-building and installations on islets in the disputed waters flared on Tuesday, when two Chinese warplanes carried out, what the Pentagon called, an “unsafe” intercept of a US military reconnaissance aircraft.

“They’re building a massive fortress in the South China Sea. They’re not supposed to be doing that,” Trump said, without saying what he would do about it.

At least, according to Mansingh, China’s leaders and Trump shared the mentality of dealmakers, which could help settle diplomatic wrangles before they get out of hand.

Jia Qingguo, an adviser to China’s government on foreign affairs, said Trump sounds like an “isolationist” who doesn’t want the United States to become too active internationally.

“So, he doesn’t sound that aggressive,” said Jia, the dean of the School of International Relations at China’s elite Peking University. “Chinese tend to think that too much so-called internationalism on the part of the US is not that good.”

A senior Japanese government official said Washington could lose influence in Asia if there was any perception it was softening its stance on issues like the South China Sea.

“And it would be very difficult to get it back,” he warned.

Mansingh said those fears are overblown as the United States self-interest lay in protecting access to the Pacific and Indian Oceans: “What would American withdrawal mean, does it want to hand over the affairs of the world to China? Would that serve anybody’s interest? I don’t think so.”

There are also fears that the TPP could unravel, or become worth a lot less to Asian partners, should Trump renegotiate the pact, as he has said he wants to do.

The deal has yet to be ratified, but US President Barack Obama has warned that delay could allow China to steal a march through its own proposed regional trade deal with 15 other nations.

“I think it’s hard to imagine that TPP would survive a Trump presidency,” said a top trade official in a major country in the region, who declined to be more closely identified.

“’Less intervention’ would be a small benefit compared to the massive damage to the world from a USA that becomes more isolationist and more crassly commercial under Trump,” he said.

The lack of priority Trump appears to give to issues that don’t serve his “America first” agenda could mean he’ll soft-pedal on human rights and democratic values, some critics said. That would come at a time when generals are running Thailand, a ‘strong man’ has just been elected the new president of the Philippines, and Malaysia’s prime minister has silenced independent media.

“Let’s hope that someone on his team realises that respect for human rights must be a core US foreign policy value, and not just a reality show line,” said Phil Robertson, deputy director for Human Rights Watch’s Asia division.

On the other hand, Panitan Wattanayagorn, an adviser to Thailand’s Defence Minister Prawit Wongsuwon expressed confidence that Trump wouldn’t apply pressure to countries like his.

“All in all, if Trump arrives, the chances of stronger ties will be good because he would want allies,” said Panitan.