US President Joe Biden who left for South Korea and Japan on Thursday to hold US leadership in Asia amid fears of a North Korean nuclear test during his trip.

It is reported that Biden wants the trip to build on recent moves accelerating a years-long US pivot to Asia, where rising Chinese commercial and military power is undercutting Washington’s dominance.

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But highlighting competing demands from Europe, Biden met right before his departure with the leaders of Finland and Sweden to celebrate their applications for joining NATO — a seismic development sparked by Russia’s invasion of Ukraine.

Meanwhile, the White House said Biden would put his signature while in Asia on a massive, $40 billion Ukraine weapons and aid package passed on Thursday by Congress.

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Signing the bill “expeditiously” will ensure no gap in the funding flow, National Security Advisor Jake Sullivan told reporters aboard Air Force One en route to Seoul.

A separate crisis awaits Biden on arrival, however — jitters that North Korea’s unpredictable leadership will choose his trip as the moment to test a nuclear capable missile or even a test nuclear explosion.

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Despite the rise in the number of Covid-19 cases, Pyongyang’s “preparations for a nuclear test have been completed and they are only looking for the right time,” South Korean lawmaker Ha Tae-keung said after being briefed by Seoul’s spy agency.

Sullivan said there was “real risk of some kind of provocation while we’re in the region, whether in South Korea or Japan.”

“We know what we will do to respond to them. We have communicated with not just our allies, but also with China,” he said.

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On Sunday, the US President will head to Japan from South Korea. He will hold talks with the leaders of both countries, as well as joining a regional summit of the Quad — a grouping of Australia, India, Japan and the United States — while in Tokyo.

During the first leg, he will visit US and South Korean troops, but will not make the traditional presidential trek to the fortified frontier known as the DMZ between South and North Korea, the White House said.

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Hours ahead of Biden arriving, South Korea’s newly elected, strongly pro-US President Yoon Suk-yeol signalled a warm welcome, tweeting: “A mountain shows its way to the summit to those who seek it. I am confident the ROK-US alliance that seeks to uphold the values of democracy and human rights shall only elevate in the future.”