President Donald Trump will take the unusual step of summoning all 100 senators to the White House on Wednesday for a briefing on the continued concern over North Korea.

The senators will be briefed by Rex Tillerson, the secretary of state, and James Mattis, the defence secretary. Dan Coats, director of national intelligence, and General Joseph Dunford, chairman of the joint chiefs of staff, will also speak to the assembled politicians.

And, while top administration officials routinely travel to Capitol Hill to address members of Congress on foreign policy and national security matters, it is unusual for the entire 100-member Senate to go to such an event at the White House, and for those four top officials to be involved.

News of the meeting came shortly after Nikki Haley, US ambassador to the UN, outlined American “red lines” in their dealings with the rogue state.

Asked when the US would strike, she replied: "If you see him attack a military base, if you see some sort of intercontinental ballistic missile, then obviously we're going to do that."