By Agence France-Presse
The precise contents of the letter, which came from Kim Yong Chol, vice chairman of North Korea's ruling party, were not known, the Post said.
Pompeo received it Friday and showed it to President Donald Trump. They concluded it was belligerent enough to call off the visit, the Post said late Monday, quoting two administration officials.
In pulling the plug on the visit, Trump tweeted that he had not seen sufficient progress toward Pyongyang denuclearizing.
Trump acted amid independent reports that North Korea has done little or nothing to roll back its nuclear program, despite promises made at a historic summit in June with Kim Jong Un.
Trump also blasted China for not doing enough to help push denuclearization, but left open the possibility of a Pompeo trip to Pyongyang when the US-China trading relationship is "resolved."