TOKYO: The peace process between the United Statesinfo-icon and North Koreainfo-icon was in crisis on Sunday after Pyongyang angrily rejected Washington's "gangster-like" demand for rapid nuclear disarmament, despite two days of intense talks.

USinfo-icon Secretary of State Mike Pompeo is in Tokyo to brief his Japanese and South Korean counterparts on the talks, which he called positive and declined to comment on Pyongyang's statement rejecting his efforts and appealing to US President Donald Trumpinfo-icon to revive the peace process.

In a tweet, Pompeo said he had held a "constructive meeting" with his Japanese counterpart and discussed "maintaining maximum pressure" on North Korea.

He is due to meet Japaninfo-icon's Prime Minister Shinzo Abe, as well as South Korean Foreign Minister Kang Kyung-wha later on Sunday.

Speaking privately, US officials suggested the harshly-worded North Korean statement was a negotiating tactic. But after two days of theatrical amity in Pyongyang, it appeared to mark a return to the North's traditional hardline position.

The North's foreign ministry took exception to Pompeo's effort to secure concrete commitments to back leader Kim Jong Un's promise, made at a summit last month with US President Donald Trump, to work towards the "denuclearisation of the Korean peninsula".

And it did so in stark terms, according to a statement relayed by the KCNA state news agency.

"The US is fatally mistaken if it went to the extent of regarding that the DPRK would be compelled to accept, out of its patience, demands reflecting its gangster-like mindset," the statement said, referring to North Korea by its official initials.

Pyongyang noted that it had already destroyed a nuclear test site -- a concession that Trump has publicly hailed as a victory for peace -- and lamented that Pompeo had proved unwilling to match this with US concessions.