Kim Yong Chol is one of the vice-chairmen of the Workers' Party of Korea, the communist organisation through which the ruling family controls North Korea, but is not technically the No. 2 behind Kim Jong Un.
He has, however, emerged as one of the leader's closest aides and has been at all the talks this year that have led to the current rapprochement.
He will be the highest-ranking North Korean to visit the United States since General Jo Myong Rok went to the White House to see President Bill Clinton in 2000, part of a denuclearisation effort that went nowhere.
There had been speculation that Kim, who greeted US Secretary of State Mike Pompeo in Pyongyang this month, would be travelling to the US amid frenzied talks aimed at salvaging the summit, scheduled to be held in Singapore on June 12.
While Pompeo is based in Washington, the North Korean diplomats accredited to the United Nations are based in New York and are not allowed to travel outside the city without special dispensation, making it the easiest place for meetings to be held.
Pompeo plans to head to New York later this week to meet Kim Yong Chol, White House press secretary Sarah Huckabee Sanders said.
Although Trump has not officially announced that the summit, which he abruptly cancelled last week, is back on, his staff is acting as though it is.
During a television interview in Washington, White House counsellor Kellyanne Conway said that if the summit does not take place on June 12, it could be held shortly afterward.
"Let's see what happens, as the President says," Conway said during an appearance on Fox News. "If he's satisfied, it will go forward."
She credited a letter from Trump last week announcing the cancellation of the summit for creating the "kinetic energy" needed to get the parties talking more seriously.
A team led by Sung Kim, a former American negotiator with North Korea who currently serves as ambassador to the Philippines, was due to hold another round of talks today on the northern side of the demilitarised zone that separates the two Koreas.
Officials began discussing the substance of any summit agreement, focusing on the thorny issue of denuclearisation, with a North Korean team led by Vice-Foreign Minister Choe Son Hui.
Separately, an advance team headed by White House Deputy Chief of Staff Joe Hagin is in Singapore making logistical plans for the summit, should it go ahead. The North Korean side is led by Kim Chang Son, who effectively serves as chief of staff to Kim Jong Un.
Kim Chang Son was seen at Beijing Airport and, asked by Japanese reporters if he was heading to Singapore for talks with US officials, he said he was "going there to play."
Now, it appears that Pompeo is getting ready for another round of discussions with Kim Yong Chol. Both are former spy chiefs and met in Pyongyang during the secretary of state's visits there in April and again this month.
Kim Yong Chol was directly sanctioned by the Treasury Department for his involvement in North Korea's nuclear programme and illicit activities while he served as director of intelligence, so the US would have had to grant a waiver to allow him to enter the country.
He now serves as head of the United Front Department, the arm of the ruling Workers' Party that handles relations with South Korea. In this role, he travelled to the South in February during the Winter Olympics, which provided the springboard for the current diplomatic frenzy, and was prominent during an inter-Korean summit on April 27.
He is widely believed to have masterminded the attack on a South Korean naval corvette, the Cheonan, in 2010, leading to the deaths of 46 sailors.
As the rapprochement with the United States has picked up pace, Kim Yong Chol appears to have taken on a broader remit to deal with the Trump Administration.
He holds a number of senior positions within North Korea's communist hierarchy. He is a member of the Workers' Party Politburo and the powerful State Affairs Commission, and he also serves on the presidium of the Supreme People's Assembly.
"This combination of positions in the party and state makes Kim one of the most powerful figures in North Korea," according to North Korea Leadership Watch, a website that tracks senior regime figures."
