US President Donald Trump ramped up his tough rhetoric against North Korea when he arrived in Japan on Sunday, saying that the United States and its allies are prepared to defend freedom and that "no dictator" should underestimate US resolve.

Trump kicked off a 12-day Asian trip and is looking to present a united front with Japan against North Korea through meetings with Prime Minister Shinzo Abe amid heightened tensions over Pyongyang's nuclear and missile tests.

He told reporters on Air Force One en route to Asia that North Korea would figure prominently in discussions during the trip. He also singled out trade, which he said had been "badly handled" in the region for years.

Trump has rattled some allies with his vow to "totally destroy" North Korea if it threatens the United States and his dismissal of North Korean leader Kim Jong Un as a "rocket man" on a suicide mission.

A top aide said last week Trump intends to tell Asian leaders the world is "running out of time" in dealing with the nuclear crisis on the Korean peninsula.

"No dictator, no regime, no nation should ever underestimate American resolve," Trump told hundreds of cheering US and Japanese troops in camouflage uniforms gathered at Yokota Air Base, just west of Tokyo, soon after he arrived.

"Every once in a while, in the past, they underestimated us. It was not pleasant for them, was it?" said Trump, who wore a bomber jacket as he addressed the troops.

North Korea's recent actions, including several missiles that flew over Japan and Pyongyang's sixth and largest nuclear test, have raised the stakes in the most critical international challenge of Trump's presidency.

Recent drills over South Korea by two US strategic bombers have further heightened tensions.

"We will never yield, never waver and never falter in defence of our freedom," Trump said.

He told reporters earlier on Air Force One that a decision would be made soon on whether to add reclusive North Korea to a list of state sponsors of terrorism.

Trump said his administration planned to take a different approach after years of what he termed "total weakness."

"We want to get it solved. It's a big problem for our country and the world, and we want to get it solved."

In an apparent attempt to distinguish between North Korea's leadership and ordinary people, he said he thought North Koreans were "great people."

Source: Khaleej Times