South Korea urged the United States to help dial down tensions with the North on Monday, after Pyongyang accused President Donald Trump of declaring war.

"It is very likely that North Korea will conduct further provocations," South Korean Foreign Minister Kang Kyung-wha said in a speech in Washington.

"It is imperative that we, Korea and the US together, manage the situation... in order to prevent further escalation of tensions or any kind of accidental military clashes which can quickly go out of control."