Undeterred by a blistering rebuke of his efforts to forge a denuclearisation deal with North Korea, US Secretary of State Mike Pompeo on Sunday appealed for North Korea’s leadership to follow Vietnam’s path in overcoming past hostilities with the United States.

Mr Pompeo called on North Korean leader Kim Jong-un to replicate Vietnam’s “miracle” of economic growth by improving ties with the US, vowing that America keeps its promises with former foes.

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Speaking to members of the US-Vietnamese business community in Hanoi, Mr Pompeo said Vietnam’s experience since the normalisation of relations with the US in 1995 should be proof for North Korea that prosperity and partnership with the US is possible after decades of conflict and mistrust.

“We know it is a real possibility because we see how Vietnam has travelled this remarkable path,” Mr Pompeo said.

“In light of the once-unimaginable prosperity and partnership we have with Vietnam today, I have a message for Chairman Kim Jong-un: President Trump believes your country can replicate this path,” he said, repeating US President Donald Trump’s pledge to help improve North Korea’s economy and provide it with security assurances in return for Kim giving up nuclear weapons.

“It’s yours if you’ll you seize the moment. This miracle can be yours. It can be your miracle in North Korea as well,” Mr Pompeo said.

The comments came after Mr Pompeo had earlier Sunday in Tokyo brushed aside North Korea’s accusation that the US was making “gangster-like” denuclearisation demands of the North. He maintained that his third visit to North Korea on Friday and Saturday had produced results.

But he also vowed that sanctions would remain until Pyongyang follows through on Kim’s pledge to get rid of his atomic weapons.

Mr Pompeo downplayed a harshly critical North Korean statement issued after the talks in which the country’s foreign ministry bashed hopes for a quick deal and attacked the US for making unreasonable and extortionate demands aimed at forcing it to abandon nuclear weapons.

The statement was sure to fuel growing scepticism in the US and elsewhere over how serious Kim is about giving up his nuclear arsenal.

“If those requests were gangster-like, the world is a gangster,” Mr Pompeo said, noting that numerous UN Security Council resolutions have demanded that the North rid itself of nuclear weapons and end its ballistic missile program.

“People are going to make certain comments after meetings. If I paid attention to the press, I’d go nuts and I refuse to do that.”

After meeting with his Japanese and South Korean counterparts in Tokyo, Mr Pompeo said his two days of talks in Pyongyang had been productive and conducted in good faith.

But following the stinging commentary from the North, he allowed that much work remains.

“The road ahead will be difficult and challenging, and we know critics will try to minimise the work that we have achieved,” he said.

He added that his two days of talks with senior North Korean officials had “made progress” and included a “detailed and substantive discussion about the next steps towards a fully verified and complete denuclearisation.”

Those include the formation of a working group to determine exactly how North Korea’s denuclearisation will be verified and a Thursday meeting with Pentagon officials to discuss the return of remains of American soldiers killed during the Korean War.

Mr Pompeo sought to dispel suggestions that the Trump administration has backed down from demanding the complete, verifiable and irreversible dismantlement of the North’s nuclear weapons.

He said North Korea understood that denuclearisation must be “fully verified” and “final.”

South Korean Foreign Minister Kang Kyung-what said that North Korea had baulked at a written pledge for “complete, verifiable and irreversible denuclearisation” for historical reasons but stressed that the goal remained the same whether that exact phrase was used.

Fully verified, final denuclearisation “isn’t any softer in stating our shared goal of complete denuclearisation,” she said.

Despite what he described as progress, Mr Pompeo said the results so far did not warrant any easing of sanctions, which he said would be enforced “with vigour” until North Korea follows through with denuclearisation.

After Mr Trump’s historic summit with Kim in Singapore last month, the president declared the North was no longer a threat and would hand over the remains of American soldiers.

Yet three weeks later, the two sides were still divided on all the issues, including exactly what denuclearisation means and how it might be verified. The promised remains have yet to be delivered.

And just hours after Mr Pompeo arrived in Tokyo from Pyongyang on Saturday, the North blasted the new talks, saying they had been “regrettable.”