SEOUL • United States President Donald Trump assured South Korea's acting president yesterday of the US' "ironclad" commitment to defend the country, agreeing with Seoul to strengthen joint defence capabilities against North Korea.

Mr Trump's assurances came amid anxiety in South Korea over the future of the alliance with the US. During his campaign, Mr Trump cast some doubt on US defence and trade commitments, saying South Korea was not paying enough to help keep 28,500 US troops in the country.

But speaking by telephone to Mr Hwang Kyo Ahn, acting president of South Korea, Mr Trump said the upcoming visit to South Korea by Defence Secretary James Mattis reflected the close friendship of the two countries and the importance of their alliance. Mr Mattis is scheduled to visit South Korea on Thursday on his first official trip abroad, which also includes a stop in Japan.

"President Trump reiterated our ironclad commitment to defend the ROK, including through the provision of extended deterrence, using the full range of military capabilities," the White House said in a statement after Mr Trump's telephone conversation with Mr Hwang, using the initials for South Korea's official name, the Republic of Korea.

"The two leaders agreed to take steps to strengthen joint defence capabilities to defend against the North Korean threat."

Mr Hwang's office quoted Mr Trump as saying the US would cooperate with South Korea "100 per cent" and that bilateral relations would be "better than ever before".

North Korea recently warned it could conduct its first test of an intercontinental ballistic missile "any time and anywhere" in a rebuke to Mr Trump.

Although North Korea has vowed to develop the ability to attack the US with nuclear warheads and has tested missiles that can cover the Korean Peninsula and its vicinity, it has never tested a long-range missile that could fly over the Pacific.

NYTIMES