President Donald Trump has said that that a proposed summit with North Korean leader Kim Jong-un is back on - little more than a week after announcing he was pulling out of the historic summit.

A whirlwind few days of diplomacy, which included high-level meetings in Singapore, the Korean demilitarised zone (DMZ) and New York - reached its peak on Friday with a top North Koreanofficial walking into the Oval Office and handing a letter from Mr Kim to the president. 

“We will be meeting on June 12 in Singapore”, Mr Trump said after meeting for well over an hour with the highest-ranking North Korean official to visit the White House in 18 years when Bill Clinton was in office.

Kim Yong-chol - who has been sanction by the US Treasury for what intelligence services have alleged was his part in a cyberattack on Sony Pictures in 2014 - hand-delivered the letter to Mr Trump before conferring with the president and Secretary of State Mike Pompeo.

When they emerged, Mr Trump was clear that the summit would take place, and that it may not be the only one. Mr Trump said he believed North Korea wanted to denuclearise but repeatedly said a compromise would likely require multiple meetings, adding that he had told Kim Yong-chol that North Korea could "take your time."

He said they discussed lifting sanctions in exchange for North Korea giving up nuclear programme. “They want to develop as a country - that’s going to happen. I have no doubt”, Mr Trump said.

But the president backed away from the United States increasing aid in exchange, suggesting the burden should fall on South Korea, China and Japan. He also said “I really think you can” expect changes in North Korea despite Mr Kim’s totalitarian regime. “They’re incredible people”, Mr Trump said of his counterparts.

Talking about the letter Mr Trump called it "very nice" but said he had not yet read it. Earlier on Friday, the Wall Street Journalsuggestedciting an official briefed on its contentsthat the letter expressed the North Korean leaders interest in meeting "without making any significant concessions or threats."

The sight of a North Korean envoy entering the Oval Office offered a vivid contrast to the months of mutual threats that had defined 2017. Mr Trump had said the US would to rain “fire and fury” on North Korea in response to an increased number of nuclear and missile tests from Pyongyang. In return the North vowed to annihilate Guam, a US territory. Both sides have haltingly embraced a warming of relations in 2018.

It has been nearly three months since South Korean envoys arrived at the White House with an earlier letter from Mr Kim inviting Mr Trump to meet, presenting an extraordinary - and risky - opportunity to neutralise the threat of a nuclear-armed North Korea. At the end of May, Mr Trump briefly called the talks off in response to what he labelled the "tremendous anger and open hostility" of recent statements from Pyongyang before quickly pivoting to again pursue a June summit.

Before travelling to Washington, Kim Yong-chol had been in New York meeting with Mr Pompeo over two days which included dinner on Wednesday night. Kim Yong-chol, vice chairman of the North Korean ruling party's central committee, was allowed into the United States despite being on the sanctions list. He was also allowed to visit the White House despite North Korean officials not usual being allowed to travel outside the New York area where Pyongyang has  a diplomatic presence at the United Nations.

While acknowledging after Thursday’s talks that convincing Pyongyang to renounce its longstanding focus on a defensive nuclear arsenal would be a “difficult, difficult challenge”, Mr Pompeo nevertheless said both sides had made progress.

“I believe they are contemplating a path forward where they can make a strategic shift, one that their country has not been prepared to make before”, Mr Pompeo said.

As the North Korean official voyaged to the White House, diplomatic exchanges were unfolding on multiple continents in a sustained effort to propel the talks forward.

American negotiators who had travelled to a neutral site along the heavily fortified Korean border projected optimism.

“We believe that we're moving in the right direction”, America’s Ambassador to the Philippines Sung Kim - a veteran North Korea expert - reportedly told South Korea’s foreign minister.

Officials from North Korea and South Korea have also spent the last few months on peace talks, with Kim Jong-un and South Korean President Moon Jae-in having met twice since April. Both sides are pursuing the long-elusive goal of formally ending the Korean War, which concluded in a truce that fractured the peninsula into two antagonistic nations, with Mr Moon also seemingly to act as a mediator between Mr Kim and Mr Trump.

On Friday, the two sides agreed to hold military and Red Cross talks later this month aimed at reducing tensions and resuming the reunion of families separated by the 1950 to 1953 war.

During a meeting of senior officials at the border village of Panmunjom, the North and South also agreed to establish a liaison office at the town of Kaesong, and to discuss fielding combined sports teams at the Asian Games in August.

South Korea's unification ministry said the Koreas agreed to set up the liaison office at a factory park in Kaesong that had been jointly operated by the countries until the South shut it down in February 2016 after a North Korean nuclear test.

The Koreas agreed to hold the military talks at Panmunjom on June 14 and the Red Cross talks on June 22 at the North's Diamond Mountain resort.

“We will hold discussions with the North so that we can implement the agreements between the two leaders with pace and without hitches and also create a positive atmosphere for the leaders' summit between North Korea and the United States”, South Korean unification minister Cho Myoung-gyon told reporters.