President Donald Trump said Thursday that he remains open to meeting with North Korean leader Kim Jong Un, hours after he canceled their planned summit in Singapore in a letter released by White House officials. >> Read more trending news “I believe that this is a tremendous setback for North Korea and, indeed, a setback for the world,” Trump said Thursday at a news conference. “I hope that Kim Jong Un will ultimately do what is right not only for himself, but perhaps most importantly what is right for his people, who are suffering greatly and needlessly.” He added that “our military ... is ready,” should North Korean officials respond to Thursday’s cancellation with a show of force. Japanese and South Korean officials have also vowed to respond if “foolish or reckless acts be taken by North Korea,” Trump said. Still, the president didn’t rule out the possibility of meeting with Kim. “A lot of things can happen, including the fact that, perhaps, it’s possible the existing summit could take place or a summit at some later date,” Trump said. “Nobody should be anxious. We have to get it right.” The president wrote in his letter to Kim that his decision to cancel the planned June 12 meeting came “based on the tremendous anger and open hostility” displayed in a recent statement from North Korea. >> From Jamie Dupree: President Trump scraps summit meeting with Kim Jong Un In the statement, the North Korean government referred to Vice President Mike Pence as a 'political dummy' and said it is just as ready to meet in a nuclear confrontation as at the negotiating table. “I feel it is inappropriate, at this time, to have this long-planned meeting,” Trump wrote. “Please let this letter serve to represent that the Singapore summit, for the good of both parties but to the detriment of the world, will not take place.” Senior North Korean diplomat Choe Son Hui told North Korea’s state-run news agency on Thursday that, “Whether the U.S. will meet us at a meeting room or encounter us at nuclear-to-nuclear showdown is entirely dependent upon the decision and behavior of the United States,” The Associated Press reported. >> Reports: North Korea demolishes nuclear test site Trump responded to the comment in his letter Thursday, telling Kim that, “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.” The letter was released just hours after reports surfaced that North Korea had demolished a nuclear test site in the country's northeast region. The closing of the testing site had been announced as a step leading up to the summit between President Donald Trump and North Korea’s leader Kim Jong Un, the Associated Press reported. Trump earlier this month announced that a historic meeting between him and Kim would take place in Singapore in June. Read the full letter released Thursday by White House officials: Check back for updates to this developing story. The Associated Press contributed to this report.