The US Secretary of State Mike Pompeo’s visit to North Korea was canceled, after a belligerent letter from Pyongyang was received, The Washington Post reported.

According to the source, the letter was sent by the former head of North Korea’s spy agency, Kim Yong Chol, but it was not known how it was sent.

The Washington Post noted the exact contents of the message were unclear, but it was sufficiently belligerent that Trump and Pompeo decided to call off the planned trip.

Trump said that he urged Pompeo to postpone the visit due to the lack of sufficient progress in the denuclearization process by Pyongyang.