US President Donald Trump and South Korean President Moon Jae-in held talks by telephone on Friday over North Korea ahead of a planned summit between the American leader and Kim Jong Un later this year. Trump and Moon expressed "cautious optimism" that North Korea could enjoy a "brighter future" after the summit, which is being eyed before the end of May. They said the North must follow "the correct path" and that they would maintain "maximum pressure" on Kim before the possible talks. A White House statement said Trump and Moon discussed preparations for their upcoming engagements with Pyongyang and agreed that “concrete actions,” not words, were the key to denuclearization of the Korean peninsula. North Korea has yet to confirm that it issued an invitation for Trump to meet Kim for nuclear disarmament talks, as South Korean officials reported to Trump during a White House meeting last week. Earlier, Moon’s chief of staff, Im Jong-seok, said proposed North-South talks in late March would cover key agenda topics and other details of the pending summit between Moon and Kim. If North Korea agrees to the talks, they would offer an opportunity for Pyongyang to break its silence on what Seoul says is Kim’s desire to meet Trump and Moon and his willingness to freeze his country’s nuclear and missile programs. “We’ve decided to narrow down the agenda topics to denuclearizing the Korean peninsula, securing permanent peace to ease military tension and new, bold ways to take inter-Korean relations forward,” Im, the head of South Korea’s summit preparation team, told reporters. Im said Moon may meet Trump after an inter-Korean summit but before Trump’s planned summit with Kim. Senior South Korean officials met Kim Jong Un in Pyongyang this month and told Washington the North Korean leader was open to giving up his nuclear weapons if North Korea’s security was guaranteed. North Korea’s state media has yet to comment on the content of Kim’s meeting with the South Koreans, but North Korean Foreign Minister Ri Yong Ho arrived in Sweden this week for talks with his Swedish counterpart Margot Wallstrom, prompting speculation that he could lay the groundwork for a Trump-Kim summit. Wallstrom’s press secretary Pezhman Fivrin said the talks, which had been due to end late on Friday, would continue on Saturday. He declined to give further information. Swedish Prime Minister Stefan Lofven said on Friday that Sweden, whose embassy represents US interests in Pyongyang, was ready to act as a facilitator to help resolve tensions. South Korea’s Foreign Minister Kang Kyung-wha was in Washington on Friday for talks expected to focus on North Korea and trade, as was Japanese Foreign Minister Taro Kono, who met US Deputy Secretary of State John Sullivan in the morning.