US President Donald Trump on Thursday played down the chances of a quick deal in getting North Korea to abandon its nuclear arms as a delegation from Pyongyang headed to meet him with a letter from North Korean leader Kim Jong Un, suggesting a proposed summit may be back on. Trump told Reuters he was still hoping for an unprecedented meeting with Kim on June 12 in Singapore to push for North Korean "denuclearization," but North Korea's leader said his position on that central issue had not changed. "I\u2019d like to see it done in one meeting," Trump said in an interview on Air Force One. "But often times that\u2019s not the way deals work. There\u2019s a very good chance that it won\u2019t be done in one meeting or two meetings or three meetings. But it\u2019ll get done at some point." In Pyongyang, Kim gave no indication of any shift on denuclearization, saying his country's will to see it realized on the Korean peninsula remained "unchanged, consistent and fixed," and that he hoped North Korea-U.S. relations and denuclearization of the peninsula would both be solved on a "stage-by-stage" basis. The official Korean Central News Agency said Kim made the remarks in a meeting with Russian Foreign Minister Sergei Lavrov and that the two agreed their countries should hold a bilateral summit next year. Until this year, Kim had made no visits outside his country since taking over from his father as leader in 2011. He has since held summits with South Korea and made two visits to China as part of a campaign of diplomatic outreach aimed at easing Pyongyang's isolation and U.S.-led international sanctions. North Korea has rejected U.S. calls for its unilateral nuclear disarmament and argued for a "phased" approach to denuclearization of the entire Korean peninsula, which in the past has meant removal of the U.S. nuclear umbrella protecting South Korea and Japan. U.S. Secretary of State Mike Pompeo said a North Korean delegation, headed by high-ranking official Kim Yong Chol, with whom he held two days of talks with in New York, would make a rare visit to the White House on Friday and give Trump a letter from Kim. The letter appeared to be in response to a comment from Trump last Thursday when he canceled the summit, accusing Pyongyang of hostility, but urged the North Korean leader to "call me or write" if he had a change of heart. Kim's letter seemed to be a sign that the summit might now go ahead. There has been a flurry of diplomatic efforts in the past few days to get it back on track. North Korea, whose nuclear ambitions have been a source of tension for decades, has made advances in missile technology in recent years and its nuclear arsenal now threatens the United States. Trump has sworn not to allow it to develop nuclear missiles that could hit the United States. He wants North Korea to give up its nuclear arms in return for sanctions relief, but the Pyongyang leadership has seen the nuclear program as crucial to its survival and says it cannot give it up without security guarantees. The North Korean visit to the White House would be the first by a high-level official from the secretive state since 2000, when senior figure Jo Myong Rok met President Bill Clinton in a previous round of U.S. disarmament efforts that failed to bear fruit. 'REAL PROGRESS' While Trump has put great importance on sealing a nuclear deal with North Korea, he has bucked traditional U.S. foreign policy by alienating America's European and NATO allies. He snubbed France, Germany and Britain by pulling out of a nuclear agreement with Iran and upset the Europeans, as well as neighbors Canada and Mexico, with protectionist trade policies meant to safeguard U.S. jobs. Trump and autocratic North Korean leader Kim traded insults and threats of war last year. But in March, the bellicose rhetoric gave way to a proposal for a historic summit. Pompeo warned at a news conference after talks with Kim Yong Chol in New York on Wednesday and Thursday that the path to better relations would not be easy. "This is going to be a process that will take days and weeks to work our way through," he said. On the subject of a summit, he said: "It does no good if we are in a place where we don\u2019t think there is real opportunity to place them together,\u201d but added: "We have made real progress toward that in the last 72 hours." Kim Yong Chol is a close aide of Kim Jong Un and is vice chairman of the ruling Workers' Party's Central Committee. The United States and South Korea blacklisted the official for supporting North Korea's nuclear and missile programs in 2010 and 2016, respectively. He has been granted special permission for official travel to the United States. During his tenure as a senior intelligence official, Kim was accused by South Korea of masterminding deadly attacks on a South Korean warship and an island in 2010. U.S intelligence linked him to a cyber attack on Sony Pictures in 2014. North Korea denied any involvement in both attacks. The United States and South Korea have technically been at war with the North for decades, even though the Korean War's combat ended in 1953, because a peace agreement was never signed, only an armistice. China, North Korea's main trading partner and ally, said it supported and encouraged the "emerging good faith" between the United States and North Korea. "At the same time as working to achieve the goal of denuclearization, we should also build long-term and effective initiatives to keep peace on the Korean peninsula," Chinese Foreign Ministry spokesman Hua Chunying said in Beijing.