WASHINGTON — The United States' policy on North Korea remains unchanged, a White House official said Tuesday, while reaffirming U.S. President Donald Trump's openness to dialogue with North Korean leader Kim Jong-un "without any preconditions." The official made the remarks in response to Yonhap News Agency's question about whether the White House has been seriously preparing for a potential Trump-Kim summit, amid questions about whether Trump would continue to pursue the North's denuclearization or shift toward goals short of denuclearization, such as tension reduction. "U.S. policy on North Korea has not changed. President Trump remains open to talking with Kim Jong-un without any preconditions," the official said in an email. The official pointed out that in his first term, Trump held three summits with Kim that "stabilized the Korean Peninsula." Questions about whether the Trump administration would stick to the denuclearization goal resurfaced after Trump said last month that North Korea has 57 "very powerful" nuclear weapons, while declining to answer a question about whether his