A senior North Korean official is headed to New York for talks with US Secretary of State Mike Pompeo, the latest indication that an on-again-off-again summit between President Donald Trump and North Korea's leader may go ahead next month.

"We have put a great team together for our talks with North Korea," Mr Trump said in a Twitter post today.

"Meetings are currently taking place concerning Summit, and more. Kim Young (sic) Chol, the Vice Chairman of North Korea, heading now to New York. Solid response to my letter, thank you!"

We have put a great team together for our talks with North Korea. Meetings are currently taking place concerning Summit, and more. Kim Young Chol, the Vice Chairman of North Korea, heading now to New York. Solid response to my letter, thank you! — Donald J. Trump (@realDonaldTrump) May 29, 2018

Kim Yong Chol, vice chairman of the ruling Workers' Party's Central Committee and formerly head of a top North Korean military intelligence agency, will meet with Mr Pompeo later this week, the White House said.

"The United States continues to actively prepare for President Trumps expected summit with leader Kim in Singapore," it said in a statement.

The North Korean envoy was scheduled to fly to the United States tomorrow after speaking to Chinese officials in Beijing, South Korea's Yonhap news agency said.

The talks show that planning for the unprecedented summit, initially scheduled for 12 June, is moving ahead after Mr Trump called it off last week in a letter to the North's leader, Kim Jong Un.

A day later, Mr Trump, who frequently exchanged insults with Kim Jong Un before they began talking about a summit, said he had reconsidered and officials from both countries were meeting to work out details.

Kim Yong Chol will be the most senior North Korean official to meet top officials for talks in the United States since Jo Myong Rok, a marshal, met then-President Bill Clinton at the White House in 2000.

Kim Yong Chol coordinated the North Korean president's two meetings with Mr Pompeo in April and May.

Kim Yong Chol is due to have talks with US Secretary of State Mike Pompeo

North Korea has faced years of isolation and economic sanctions over its nuclear and missile programmes since it conducted its first nuclear test in 2006.

The North had tested missiles believed to be capable of reaching the United States but Mr Trump has vowed not to let Pyongyang develop one that could deliver a nuclear warhead.

North Korea has rejected US demands for it to unilaterally abandon its nuclear programme.

It defends its nuclear and missile programmes as a deterrent against what it sees as US aggression.

The United States stations 28,500 troops in South Korea, a legacy of the 1950-53 Korean War.

This week's talks and meetings on the border between North and South Korea are aimed at determining whether North Korea is prepared to make sufficient commitments toward getting rid of its nuclear weapons, a US official said.

Kim Jong Un has sent favourable signals in recent days and Mr Trump’s aides will soon assess whether he is willing to take serious steps before making a final decision on whether to go ahead with the summit, the official said, speaking on condition of anonymity.

Kellyanne Conway, a top adviser to Mr Trump, told Fox News a summit might not take place on the date originally set, but perhaps might go ahead shortly after.

Meanwhile, North Korean leader Kim's de facto chief of staff, Kim Chang Son flew to Singapore via Beijing late yesterday, Japanese public broadcaster NHK reported.

Kim Yong Chol is due to have talks with US Secretary of State Mike Pompeo

At the same time, a "pre-advance" US team was in Singapore to meet North Koreans.

But events have moved quickly since Mr Kim made a conciliatory New Years address at the end of last year, following months of sharply rising tension and war-like rhetoric between Mr Trump and Mr Kim.

The latest flurry of diplomacy began on Saturday, when Mr Kim and South Korean President Moon Jae-in held a surprise meeting on at the border village of Panmunjom, during which they agreed the North Korea-US summit must be held.

On Sunday, the US State Department said US and North Korean officials had met at Panmunjom.

Sung Kim, the former US ambassador to South Korea and current ambassador to the Philippines, led the US delegation, an official told Reuters.

He will meet North Korea's foreign ministry official Choi Sun Hee again tomorrow on the border, Yonhap reported, citing a diplomatic source, adding that the agenda for the Trump-Kim summit would be roughly worked out.