WASHINGTON (Reuters) -- US President Donald Trump called off a visit to North Korea by Secretary of State MikePompeo after the latter received a belligerent letter from a senior North Korean official just hours after the trip was announced last week, the Washington Post reported on Monday.

The Post quoted two unnamed senior US administration officials as saying the letter came on Friday from Kim Yong-chol, vice chairman of North Korea’s ruling Workers’ Party Central Committee, who led previous rounds of talks with Pompeo.

The newspaper said the exact contents of the message were unclear, but it was sufficiently belligerent that Trump and Pompeo decided to call off the journey.

The planned trip had been announced the previous day for this week and Pompeo had intended to introduce a newly named special envoy, Stephen Biegun, to his North Korean counterparts.The White House referred queries on the Washington Post report to the State Department, which did not immediately respond to a request for comment.

In cancelling Pompeo‘s trip, Trump publicly acknowledged for the first time that his effort to get North Korea to denuclearize had stalled since his June 12 summit with its leader, Kim Jong-un. On Sunday, North Korea’s state media accused the United States of “double-dealing” and “hatching a criminal plot” against the country, but did not mention Pompeo‘s canceled visit. US intelligence and defense officials have repeatedly expressed doubts about North Korea’s willingness to give up its nuclear weapons and did not expect Pompeo‘s trip to yield positive results.