US President Donald Trump touted North Korea's "AWESOME" future if his "friend" Kim Jong Un, whom he meets for a high-stakes dinner later today, agrees to give up his nuclear arsenal.

Trump's upbeat message came in a tweet hours before a second summit in Hanoi to build on the pair's first meeting in Singapore in June.

The president risked being distracted by scandal back in Washington, where his former lawyer Michael Cohen was set to describe him as a "con man" in testimony to Congress scheduled for shortly after Trump's dinner ends.

Trump, seeking a big foreign policy win to push back against domestic troubles, believes his unique brand of personal diplomacy and business acumen can make history.

His goal is to persuade Kim to dismantle his nuclear weapons and resolve a stand-off with the totalitarian state that has bedevilled US leaders since the end of the Korean war in 1953.

To lure Kim into radical change, Trump is believed to be considering offering a formal peace declaration -- though not a treaty -- to draw a line under the technically still unfinished war.

But Washington faces mounting pressure to extract significant concessions from Kim, who has so far shown little desire to ditch the nuclear capability.

China's Foreign Minister Wang Yi said today the Hanoi meeting could be "an important step towards advancing the denuclearisation" of the Korean peninsula.

While the Singapore summit ended with a statement promising to work "towards" denuclearisation, Washington and Pyongyang disagree on what that even means.

And while North Korea has now gone more than a year without conducting missile and nuclear tests, it has done nothing to roll back the weapons already built.

BUSINESSMAN'S BIG PITCH         

Trump, a former real estate tycoon who often boasts of being one of the world's best negotiators, is pitching a vision of North Korea as a new Asian economic tiger if it surrenders its nuclear status.

He said the country could one day emulate Vietnam -- a communist state once locked in devastating conflict with the United States, but now a thriving trade partner.

And he has invested himself personally in the relationship with Kim, creating the diplomatic equivalent of a Hollywood odd-couple bromance.

Before Singapore, they were slinging bizarre insults -- Trump calling Kim "rocket man" and Kim calling him a "dotard."

With North Korea then busily testing missiles and conducting underground nuclear tests, analysts feared the duo were egging each other on towards a catastrophic confrontation.

Now, Trump talks of "love" and claims that his ground-breaking policies defused the threat posed by Kim.

The Hanoi summit is more elaborate than the Singapore occasion. The White House said Trump and Kim will hold a 10-minute meeting before an approximately 20-minute session without aides, followed by dinner lasting around 90 minutes.

Tomorrow they are due to meet again, although no details have been released, adding to the impression that much is being decided at the last minute.

DOMESTIC WOES

Even going half-way around the world, however, has not been enough to free Trump from his mounting domestic woes.

In explosive testimony, Cohen is expected to testify under oath that Trump was repeatedly dishonest, including lying that he had no business dealings in Russia, when in reality he pursued a property deal during his successful 2016 presidential campaign.

The subject risks complicating any post-summit press conference for Trump, who responded Wednesday that Cohen "did bad things" and is "lying".

In another indication Trump's mind was not entirely on the complex task of handling Kim, he also found time today to joke on Twitter about an opposition senator's past false claims to have served in Vietnam.

The issue is something of an obsession for Trump, who mercilessly ribs Senator Richard Blumenthal, despite himself also managing to avoid being sent to fight in the war.

FOREIGN POLICY GAMBIT

Critics warn Trump is so keen to score a deal with Kim that he could give away too much, too quickly, endangering US allies South Korea and Japan.

In Singapore, Trump took his own generals by surprise when he announced a suspension of military exercises with the South -- something the North badly wanted.

Washington would ideally like Kim to dismantle a key nuclear facility at Yongbyon, allow in international inspectors, or even hand over a list of all his nuclear assets -- something the North Koreans have categorically refused to do.

In return, Trump is believed to be considering dangling relief from tough international sanctions. Opening diplomatic liaison offices is another possible US concession.

Another possibility is a joint declaration to end the Korean War, which closed with a ceasefire but no peace treaty.

Some analysts fear this hugely symbolic gesture would upset the delicate power balance in a region where the US and China are already struggling for influence.

Harry Kazianis, director of Korean Studies at the Washington-based Center for National Interest think-tank, said a peace declaration might be the "big deliverable coming out of the summit."

"If President Trump is willing to trade what amounts to a piece of paper for some plutonium -- and possibly much more -- then I think history can be made."