Donald Trump appears to threaten regime change against North Korea: 'They won't be around much longer'

US President calls North Korean leader 'Little Rocket Man'

North Korea's foreign minister had called Donald Trump 'a mentally deranged person full of megalomania and complacency' (AP/Brynn Anderson)

Donald Trump has appeared to threaten regime change against North Korea, tweeting to say if the country's foreign minister echoed the thoughts of its leader they "won't be around much longer."

North Korea's foreign minister, Ri Yong-ho, had earlier said targeting the United States mainland with its rockets was inevitable after "Mr Evil President" Donald Trump called Kim Jong-un "rocket man."

Afterwards, Mr Trump took to twitter to say: "Just heard Foreign Minister of North Korea speak at UN If he echoes thoughts of Little Rocket Man, they won't be around much longer!"

Mr Ri had called the US President "a mentally deranged person full of megalomania and complacency" who was trying to turn the UN into a "gangsters' nest."

The mudslinging came as US bombers and fighter escorts flew to the farthest point north of the border between North and South Korea by any such American aircraft had this century.

The Pentagon said the mission, in international airspace, showed how seriously Mr Trump takes the North's "reckless behaviour."

"This mission is a demonstration of US resolve and a clear message that the President has many military options to defeat any threat," Defence Department spokeswoman Dana White said.

"North Korea's weapons program is a grave threat to the Asia-Pacific region and the entire international community. We are prepared to use the full range of military capabilities to defend the US homeland and our allies," she added.

North Korea has said it intends to build a missile capable of striking all parts of the US with a nuclear bomb.

Mr Trump has said he won't allow it, although the US so far has refrained from using military force to impede the North's progress.

Last week, the US President announced more economic sanctions against the impoverished and isolated country, targeting foreign companies which deal with the North.

In a speech at the United Nations last week, Mr Trump had issued the warning of potential obliteration and mocked the North's young autocrat as a "Rocket Man" on a "suicide mission."

His executive order expanded the Treasury Department's ability to target anyone conducting significant trade in goods, services or technology with North Korea, and to ban them from interacting with the US financial system.

Mr Trump also said China was imposing major banking sanctions, too, but there was no immediate confirmation from the North's most important trading partner.

If enforced, the Chinese action Mr Trump described could severely impede the isolated North's ability to raise money for its missile and nuclear development. China, responsible for about 90 per cent of North Korea's trade, serves as the country's conduit to the international banking system.