The President of United States Donald Trump abruptly cancelled his top diplomat’s planned trip to North Korea, publicly acknowledging for the first time that his effort to get Pyongyang to denuclearize had stalled since his summit with the North’s leader.

Trump partly blamed China for the lack of progress with North Korea and suggested that talks with Pyongyang, led so far by Secretary of State Mike Pompeo, could be on hold until after Washington resolved its bitter trade dispute with Beijing.

It was a dramatic shift of tone for Trump, who had previously hailed his June 12 summit with North Korean leader Kim Jong Un as a success and said the North Korean nuclear threat was over, despite no real sign Pyongyang was willing to give up its nuclear weapons.

But Trump still kept the door open to a second summit with Kim, with whom the president recently said he has “great chemistry.””I have asked Secretary of State Mike Pompeo not to go to North Korea, at this time, because I feel we are not making sufficient progress with respect to the denuclearization of the Korean Peninsula,” Trump wrote on Twitter.

Pompeo has pressed for tangible steps toward North Korea’s abandonment of its nuclear arsenal while Pyongyang is demanding that Washington first make concessions of its own.

Trump’s statement came just a day after Pompeo said he would again visit North Korea and would take his new special envoy, former auto industry executive Stephen Biegun, with him.