By Agencies

US top diplomat pushes back at Pyongyang's claim that it would get concessions from Trump during 'step-by-step' process.

US Secretary of State Mike Pompeo has said that there will be no sanctions relief for North Korea until it has denuclearised in a way that is "complete, verifiable and irreversible".

The US top diplomat was in South Korea on Thursday to brief South Korean President Moon Jae-in on this week's landmark summit between US President Donald Trump and North Korean leader Kim Jong-un.

Pyongyang understood the need for a "quick" denuclearisation process which would be based on "conditions" and "sequencing," Pompeo said following joint talks in Seoul with his South Korean and Japanese counterparts, Kang Kyung-hwa and Taro Kono respectively.

Pompeo's comments came after North Korean state media reported on Wednesday that Trump had agreed to a "step-by-step" process, suggesting that North Korea would gain concessions from the US at the same time.

Pompeo had told reporters on Wednesday that the North Korean nuclear disarmament could take two years to complete.

Trump also declared on social media on Wednesday that "there is no longer a nuclear threat from North Korea", after his meeting with Kim.

"Everybody can now feel much safer than the day I took office," he wrote on Twitter.

Before the talks with Pompeo, Moon on Thursday hailed the summit as a great success.

While acknowledging that there may be "very conflicting views regarding the outcome of the summit," the US had been able to spare "the whole world... the fear of war - a nuclear war - as well as the long-range missiles," he said.

By referencing the "conflicting views", Moon appeared to be referring to Trump's unexpected promise to halt joint military exercises with South Korea, which the US president called a "provocation" to the North.

The announcement apparently caught US allies including Seoul as well as the US military off guard.

Japan has expressed concern, while South Korea said earlier it needed "to find out the exact meaning and intention of President Trump's remarks."

'Deal lacks in details'

But Trump's move had long been suggested by China, and Beijing was quick to applaud its announcement on Wednesday.

The agreement signed by Trump and Kim on Tuesday said the US would provide security guarantees to North Korea, while Pyongyang committed to denuclearisation.

But details on what form those promises would take were sparse, with critics noting the lack of a timeline for when North Korea will begin dismantling its nuclear programme.

In an interview recorded in Singapore but broadcast on the US television channel, Fox News, late on Wednesday in the US, Trump said that a withdrawal of US troops from South Korea had not been discussed at the summit.

Trump said not only was a pullout not discussed, the US "is not drawing down at all."

But he also said he would love to bring the US military out of South Korea because of the cost, adding that while it was not currently part of the discussion, "at the appropriate time, it will be". 

Such a withdrawal would be problematic for Japan, to which the US has long provided security assurances, while it would be welcomed by China, which wants to expand its influence in the region.

Pompeo is expected in Beijing later on Thursday to update Chinese officials on the Singapore summit.

As an "important party," China offered to assist North Korea and the US in further talks and in implementing decisions made at the summit.

Observers expect a visit by a North Korean official to Beijing soon, as the traditional allies will want to consult going forward.

The two Koreas were also to hold the first high-level military talks in 10 years on Thursday, according to the South Korean news agency Yonhap.

The talks, aimed at discussing ways of easing cross-border tensions, were to be held at the "truce village" of Panmunjom, on the border between the two countries.