WASHINGTON — The United States aspires to have North Korea as a "close partner" and not an enemy, Secretary of State Mike Pompeo said Friday, noting that the United States has often in history become good friends with former adversaries. Pompeo said he had told North Korean leader Kim Jong Un of that hope during his brief visit to Pyongyang earlier this week, during which he finalized details of the upcoming June 12 summit between Kim and President Donald Trump and secured the release of three Americans imprisoned in the country. He said his talks with Kim on Wednesday had been "warm," "constructive," and "good" and that he made clear that if North Korea gets rid of its nuclear weapons in a permanent and verifiable way, the United States is willing to help the impoverished nation boost its economy and living stands to levels like those in prosperous South Korea. "We had good conversations about the histories of our two nations, the challenges that we have had between us," Pompeo told reporters at a news conference with South Korea’s visiting foreign minister Kang Kyung-wha. "We talked about the fact that America has often in history had adversaries who we are now close partners with and our hope that we could achieve the same with respect to North Korea." He did not mention other adversaries by name, but Pompeo and others have often noted that the United States played a major role in rebuilding Japan and the European axis powers in the wake of the Second World War. With U.S. help, those countries recovered from the devastation of conflict. "If North Korea takes bold action to quickly denuclearize, the United States is prepared to work with North Korea to achieve prosperity on the par with our South Korean friends," he said. Kang praised the upcoming meeting between Trump and Kim in Singapore as an "historic" opportunity, but added a few notes of skepticism as well. Amid concerns that North Korea will demand the United States withdraw its troops from neighboring South Korea, Kang emphasized that the U.S. military presence there must be "a matter for the U.S.-ROK alliance first and foremost," using an acronym for South Korea’s official name, the Republic of Korea. She said the U.S. troop presence in the South for the past 65 years has played a "crucial role for deterrence," peace and stability on the Korean peninsula. Therefore, she said, any change in the size of the U.S. forces in the South Korea should not be on the table at the summit. "The next few weeks will be critical, requiring air-tight coordination between our two countries," Kang said, noting that South Korean President Moon Jae-in would be in Washington to see Trump later this month. Since Trump announced plans to hold a summit with Kim, questions have been raised continually about whether the two leaders have the same objective in mind when they speak about "denuclearization." To the United States, that means the North giving up the nuclear weapons it has already built. But North Korea has said it’s willing to talk now because it’s already succeeded in becoming a nuclear-armed state, fueling skepticism that the North would truly being willing to give those weapons up. Pompeo said there would need to be "complete" and "verifiable" denuclearization that would remove North Korea as a threat to the South, the United States and the rest of the world. He said a massive inspection and monitoring regime would be required to ensure the North’s compliance. "I think there is complete agreement about what the ultimate objectives are," Pompeo said, though he declined to offer more detail.