Trump: No dictator should underestimate US resolve

President Donald Trump warned on Sunday that "no dictator" should underestimate the United States, as he launched an Asia tour that will be dominated by the North Korea nuclear crisis.

Speaking to cheering military personnel at Yokota Air Base just west of Tokyo, Trump issued a threat that "no one, no dictator, no regime and no nation should underestimate... American resolve."

"Every once in a while in the past, they underestimated us. It was not pleasant for them, was it?" roared Trump.

Trump's marathon trip comes with the North Korea crisis at fever pitch, as US bombers fly sorties over the Korean peninsula and fears mount of another Pyongyang missile test.

According to the Washington Post, Pentagon officials have warned that the only way to locate and secure North Korea's nuclear weapons sites would be via a ground invasion.

The president's first stops are Japan and South Korea - frontline US allies in the effort to force Pyongyang to abandon its nuclear programme, and the two countries with most to fear should a full-scale conflict break out.

Speaking to reporters on the plane, he announced he would likely be meeting Russian President Vladimir Putin during the tour, as the international community scrambles for a solution to the North Korean crisis.

"I think it's expected we'll meet with Putin, yeah. We want Putin's help on North Korea, and we'll be meeting with a lot of different leaders," said Trump.

He added that North Korea was a "big problem for our country and for the world, and we want to get it solved" but had kind words for the people in the hermit state.