WASHINGTON —- President Trump on Friday called off a planned trip to North Korea by Secretary of State Mike Pompeo, just days before the top diplomat was to arrive in the country for the next round of high-stakes nuclear talks, the first public sign of the president’s frustration over the stalled negotiations.

In a surprise announcement on Twitter, Trump declared that he had instructed Pompeo, who was planning his fourth visit to Pyongyang, “not to go to North Korea, at this time” because there had not been “sufficient progress with respect to the denuclearization of the Korean Peninsula.”

The president left the door open for future talks, but he raised the stakes by accusing China of a lack of cooperation on the issue and appearing to tie the matter to the escalating trade war between Washington and Beijing.

“Secretary Pompeo looks forward to going to North Korea in the near future, most likely after our Trading relationship with China is resolved,” Trump wrote.

The president’s tweets marked an abrupt shift in his public posture after he insisted for weeks that progress was being made after his meeting in Singapore with North Korean leader Kim Jong Un in June. Trump has repeatedly hailed that meeting as an unqualified success, declaring that there was “no longer a Nuclear Threat from North Korea” and citing the return of what is thought to be 55 sets of remains of U.S. service members killed in the Korean War. He has decried critics who cited a lack of firm commitments.