The Pentagon chief also said North Korea’s nascent missile capabilities were “grossly overmatched” by those of the US, and that Pyongyang would lose in any arms race or conflict.

Trump earlier boasted on Twitter that America’s nuclear arsenal was “far stronger and more powerful than ever before,” after North Korea said it was considering a missile strike near the tiny US Pacific territory of Guam.

“Hopefully we will never have to use this power, but there will never be a time that we are not the most powerful nation in the world!” Trump tweeted.

Amid reports that Trump’s comments had taken his inner circle by surprise, White House spokeswoman Sarah Huckabee Sanders said the National Security Council and other officials knew the “president was going to respond… with a strong message in no uncertain terms.”

Still, Trump’s tone was at odds with that of Secretary of State Rex Tillerson, who said he did not believe “there is any imminent threat” to Guam or other US targets, and expressed hope that diplomatic pressure would prevail in the crisis.

State Department spokeswoman Heather Nauert the Trump administration was all on “the same page.”

“The president is sending a strong message to North Korea in the kind of language that North Korea understands,” she said.