After days of increasingly bellicose statements from Pyongyang, President Donald Trump on Thursday pulled the plug on a scheduled June 12 summit meeting with North Korean leader Kim Jong Un, but left the door open to future negotiations over efforts to denuclearize the Korean Peninsula. “If and when Kim Jong Un chooses to engage in constructive dialogue and actions, I am waiting,” the President said at the White House. Mr. Trump’s remarks came several hours after he sent a letter to Kim Jong Un, calling off their summit, as U.S. officials laid the blame directly on the North Koreans. “While many things can happen and a great opportunity lies ahead, potentially, I believe that this is a tremendous setback for North Korea and, indeed, a setback for the world,” the President said. I have decided to terminate the planned Summit in Singapore on June 12th. While many things can happen and a great opportunity lies ahead potentially, I believe that this is a tremendous setback for North Korea and indeed a setback for the world… pic.twitter.com/jT0GfxT0Lc — Donald J. Trump (@realDonaldTrump) May 24, 2018 Both in his letter to Kim, and in his public remarks, the President edged back toward some of the tougher rhetoric that had characterized the Kim-Trump relationship of last year, when the two men lobbed threats of possible military action. “Hopefully, positive things will be taking place with respect to the future of North Korea. But if they don’t, we are more ready than we have ever been before,” Mr. Trump said. His letter was even more direct. “You talk about your nuclear capabilities, but ours are so massive and powerful that I pray to God they will never have to be used,” Mr. Trump wrote, labeling the cancelled summit a ‘missed opportunity.’ On Capitol Hill, lawmakers asked the Secretary of State – who happened to be at a hearing of the Senate Foreign Relations Committee – what would happen next, as Secretary Mike Pompeo said the U.S. would continue with the “maximum pressure” campaign of economic sanctions against Pyongyang, and wait for the response of Kim Jong Un. Pompeo on what's next: 'It's Kim's choice. We welcome that call, that outreach.' Sounding somewhat dejected: 'In some ways, situation normal. The pressure campaign continues.' — Michelle Kosinski (@MichLKosinski) May 24, 2018 “I am hopeful that we can continue to have conversations so that we can put his back on track,” Pompeo said, though he admitted it was not clear why the North Koreans suddenly went from being willing partners to not answering phone calls. “I don’t really know I want to speculate why they took those actions, because I don’t think we know,” Pompeo added. “In some ways, it’s situation normal,” Pompeo said to one question. “The pressure campaign continues.” Secretary of State Mike Pompeo says the US wants the complete denuclearization of North Korea https://t.co/ZvF0b8XHpG https://t.co/LNKUmWLNww — CNN Politics (@CNNPolitics) May 24, 2018 Pompeo sparred with several Senate Democrats during the hearing, as he rejected assertions that the U.S. had rushed into a summit with Kim, and wasn’t really prepared to deal with a North Korean leader who is known for sudden course changes. “Unfortunately, it seems that our chief diplomat is negotiating war,” said Sen. Ed Markey (D-MA) of Pompeo. “From the beginning, when Trump impulsively decided that he would meet with Kim Jong Un, it has been clear that the summit involved very little preparation,” said Sen. Bernie Sanders (I-VT). “We cannot return to the name-calling and saber-rattling of the last year,” said Rep. Barbara Lee (D-CA).