A top North Korean official widely known as leader Kim Jong Un's right-hand man has arrived in Beijing, en route to the United States for a meeting with top U.S. officials, a report said Tuesday, as Washington and Pyongyang continue to lay the groundwork for a historic leaders' summit.

The trip to the U.S. by former spy chief and senior official Kim Yong Chol is the highest-profile visit in nearly 18 years as the two sides work to bridge gaps over Pyongyang's nuclear weapons program ahead of a planned summit between North Korean leader Kim Jong Un and U.S. President Donald Trump that had been scheduled for June 12 in Singapore.

Kim Yong Chol arrived in Beijing on Tuesday for talks with Chinese officials, South Korea’s Yonhap news agency said, and he was due to depart for New York the following day. In a tweet, Trump confirmed that Kim was heading for the United States.