Washington/Seoul, Jan 30 (IANS): US President Donald Trump reaffirmed Washington's "ironclad commitment" towards South Korea's security and agreed to take steps to bolster joint defence capabilities, the media reported on Monday.

Trump made the remark when he had a telephonic conversation with South Korea's Acting President and Prime Minister Hwang Kyo-ahn late Sunday and discussed the importance of the alliance between the two countries, the White House said in a statement.

"President Trump reiterated our ironclad commitment to defend South Korea, including through the provision of extended deterrence, using the full range of military capabilities. The two leaders agreed to take steps to strengthen joint defence capabilities to defend against the North Korean threat," Yonhap News Agency reported citing the statement as saying.

The two leaders also discussed US Defence Secretary James Mattis' upcoming visit to Seoul next week and noted the trip "reflects the close friendship between our two countries and demonstrates the importance of the US-South Korea alliance."

Hwang congratulated Trump on his inauguration and Trump wished Hwang and the South Korean people a prosperous and happy Lunar New Yeat.

The phone conversation came amid heightened tensions on the Korean Peninsula after North Korean leader Kim Jong-un threatened in his New Year's Day address to test-fire an intercontinental ballistic missile apparently capable of reaching the US.

Hwang has been serving as the acting president since President Park Geun-hye was impeached by parliament over corruption allegations on December 9.

Trump already had a phone conversation with Park in November, after his surprise election victory.