WASHINGTON (REUTERS) - United States President Donald Trump and South Korean Acting President Hwang Kyo Ahn agreed to take steps to strengthen joint defence capabilities to defend against North Korea's nuclear threat, the White House said on Sunday (Jan 30) after a telephone call between the two leaders.

"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 White House said in a statement.

It also said Trump and Hwang discussed the upcoming visit by the new US defence secretary to Japan and South Korea, where shared concerns about North Korea will top the agenda.

The United States and South Korea have agreed to deploy a Terminal High Altitude Area Defense (THAAD) system designed to protect against North Korea's growing nuclear and ballistic capabilities despite objections from China, which says the radar could penetrate Chinese territory.

North Korean leader Kim Jong Un said on Jan 1 his country was close to test-launching an intercontinental ballistic missile (ICBM), and state media has said a launch could come at any time.

North Korea has maintained its nuclear and missile programs in violation of repeated rounds of international sanctions.