HANOI - North Korea lashed out Saturday at Donald Trump's "warmonger's" tour of Asia as the US president landed in Hanoi on the latest leg of a five-nation regional visit to drum up support against Pyongyang's nuclear weapons build-up.

The outburst came as Trump nears the tail end of his sweep through Japan, South Korea, China, Vietnam and the Philippines that has seen him rail against the North's nuclear ambitions and deliver his "America First" vision of global trade.

Trump has urged the region to take a united front against the threat posed by isolated North Korea, which has sparked global alarm with its nuclear and missile tests in recent months. On Friday he warned world leaders gathered in the Vietnamese resort city of Danang that the Asia-Pacific region "must not be held hostage to a dictator's twisted fantasies".

Pyongyang issued its own retort Saturday branding Trump's Asia tour a "warmonger's visit for confrontation to rid the DPRK of its self-defensive nuclear deterrence", in the first comments on the trip by a North Korean official.

It said Trump's warnings "can never frighten us or put a stop to our advance", according to the state-run KCNA news agency, quoting a Pyongyang foreign ministry spokesman.

Tensions over the North's weapons programme have surged in recent months, as Pyongyang carried out a sixth nuclear test - by far its largest to date - and test fired dozens of missiles, some capable of reaching the US mainland.

In a speech to the South Korean parliament on Wednesday, Trump warned Pyongyang not to underestimate the United States, while offering leader Kim Jong-Un a better future if he gives up his nuclear ambitions.

Trump has also prodded Chinese President Xi Jinping to pile pressure on North Korea.

"I'd like to have him ratchet it up, and I think he's doing that," Trump told reporters aboard Air Force One en route to Hanoi Saturday following a regional trade meeting in the coastal city of Danang.

Though China has backed UN sanctions, Washington would like to see Beijing clamp down on unauthorised trade along the North Korean border.

Trump will turn his attention to Vietnam for an overnight stop in the capital of a communist country once considered a bitter enemy.

Vietnam has eagerly courted trade and investment with the US since Trump's election, more so after he yanked the US from a key Pacific region trade pact, taking with him low tariff access to the world's largest market.

The Trump administration has singled out Vietnam as one of many countries that has a yawning trade deficit with the US.

Former billionaire businessman Trump told a gathering of regional CEOs Friday he is open to doing business with Asia - but would no longer tolerate sweeping trade deals he brandished as unfair and harmful to American jobs.

Despite his tough talk on trade, he boasted about his cosy relationship with regional leaders.

"China likes me. And I get along with them, I get along with others too," he told reporters after meeting with 20 fellow heads of state at a beachside retreat in the coastal city of Danang.

"I have a great relationship with Justin Trudeau, who I just left. I'll be honest with you, I think I have a great relationship with every single one of them. Every person in that room today," he said.

He also said he had a "very good feeling... a good relationship" with Russia's Vladimir Putin.

Trump will attend a state banquet on Saturday night ahead of a welcoming and deal signing ceremony in Hanoi on Sunday with Vietnam's top leadership.

His next stop is the Philippines for a two-day visit that will include an ASEAN summit of Southeast Asian leaders, capping off the 11 day visit to Asia.

There he will hold talks with President Rodrigo Duterte, like Trump a famously outspoken world leader.