Trump in 'no rush' as formal nuke talks open with Kim

US President Donald Trump said he was in "no rush" to secure a deal over Pyongyang's nuclear programme as he kicked off formal talks Thursday with North Korean leader Kim Jong Un.

The two men who once traded personal insults and threats of destruction are holding their second meeting in eight months, with analysts warning it needs to produce more concrete progress than their initial historic get-together in Singapore.

The Singapore summit resulted in cozy images, but only a vague commitment from Kim to "work toward complete denuclearisation of the Korean peninsula". Diplomacy has since stalled amid disagreements on what that actually means.

But as they sat down for Thursday's formal discussions in Hanoi, Trump said success would come over a "longer period of time".

Multiple sanctions have been imposed on the North because of its weapons programmes and tensions soared in 2017 before a wave of detente.

For his part, Kim said there were "people who hold a sceptical view of our meeting" but he pledged to seek "great, ultimately good results".

"I think watching us have a great time will be like watching a scene from a fantasy movie," said the North Korean leader.

The two men have again displayed outward signs of an unlikely diplomatic bromance in Hanoi, clasping hands and appearing to share jokes when they first met.

On Wednesday, Trump described Kim as a "great leader" and said his country had "tremendous economic potential, unbelievable, unlimited" as he vowed to help North Korea achieve those goals.

They had a "candid and honest dialogue" during their one-on-one meeting, North Korea's state news agency KCNA said Thursday.

And over dinner, it added, "sincere and deep opinions were exchanged with a view to making comprehensive and epoch-making results".

The state-run Rodong Sinmun newspapers plastered photographs of their handshake over its front page, one of them appearing to show Trump bowing slightly as he took Kim's hand featuring prominently.

It was a far cry from the height of missile-testing tensions in 2017 when Trump slammed Kim as "rocket man" and the younger man branded the American president a "mentally deranged US dotard".

The summit was "pageantry for Trump and brings Kim more credibility on the world stage as a responsible, rational actor", the Stimson Center's David Kim told AFP.

"But I would define success in terms of outcomes. A decent outcome if we can get some concrete and verifiable commitments toward denuclearisation," he said, although the US would have to "trust but verify".

But scandal back home in Washington threatens to distract Trump with his former personal lawyer and fixer Michael Cohen calling him a "racist" and a "conman" during a congressional hearing.

The president already showed he had the testimony at the back of his mind when he tweeted about it before his first meeting with Kim, saying Cohen -- who has been sentenced to three years in jail -- was "lying in order to reduce his prison time".

Kim is looking for relief from biting sanctions for his deeply impoverished country, as well as security guarantees for him and his regime.

One carrot could be a declaration to end the Korean War, which ended in 1953 with an armistice not a formal peace treaty. Asked about that before Wednesday's dinner, Trump merely replied: "We'll see."

Also mooted is the possibility of opening liaison offices, the first step on the road to normalising diplomatic relations.

In return, Kim might pledge to destroy North Korea's decades-old Yongbyon nuclear complex, which has long been at the heart of Pyongyang's atomic development but remains shrouded in secrecy -- and North Korea has promised to mothball it twice before.

In the run-up to the Hanoi summit, however, Trump already appeared to lower expectations for the outcome, saying he was content if North Korea continued its pause in nuclear and missile testing.

In Vietnam, Trump has frequently pointed to the recent history of the host country -- once a war-torn foe of the United States, now enjoying an economic boom with growth of more than seven percent.

Hailing Kim as a "friend", he said North Korea could enjoy an "AWESOME" future if it gave up its nuclear weapons, but most analysts say that outcome is extremely unlikely.

Flag-waving crowds have welcomed the leaders in Hanoi.

"I hope North Korea will be in a better economic situation so that people there suffer less," office worker Nguyen Thi Hong told AFP. "North Korea should learn from Vietnam."