U.S. President Donald Trump agreed to meet North Korean leader Kim Jong Un by May, a South Korean official said Thursday in Washington.

Kim is committed to denuclearization and would refrain from nuclear or missile tests, South Korean National Security Council chief Chung Eui-yong told reporters at the White House. The North Korean leader also understands that routine U.S.-South Korea joint military exercises must continue, Chung said.

U.S. National Security Adviser H.R. McMaster will brief the UN Security Council on the latest developments on March 12, according to a European diplomat who asked not to be identified since the announcement isn’t public. Trump earlier surprised reporters at the White House with news that South Korean officials would be making a “major” announcement at 7 p.m. local time.

A South Korean delegation is in Washington this week briefing administration officials about their recent talks in Pyongyang, which produced speculation that the U.S. and North Korea may enter talks over Kim Jong Un’s nuclear weapons program. During their meetings in Pyongyang, North Korean officials indicated they would consider halting their nuclear weapons program if the U.S. can guarantee the safety of Kim’s regime.

U.S. Secretary of State Rex Tillerson, traveling in Ethiopia on Thursday, had tamped down hopes for a breakthrough with North Korea, saying “We’re a long way from negotiations, we just need to be very clear-eyed and realistic about it.” South Korean President Moon Jae-in made similar comments, saying “This is just a start, and we can’t be optimistic just yet.”

The U.S. and North Korea have been at loggerheads since the Korean War ended without a peace treaty almost 65 years ago, and Kim’s government has repeatedly said nuclear weapons were necessary to deter any U.S.-led military action. Over the years, the Kim dynasty has raised the prospect of abandoning its nuclear-weapons program if the U.S. gave up policies it considers hostile.

Trump and Kim traded increasingly tense barbs after the U.S. president took office in January 2017. Trump vowed to bring “fire and fury” down on North Korea if forced to do so, while Kim derided the U.S. president as a “dotard” as he ramped up his missile and nuclear tests.

Tensions appeared to ease after South Korea agreed to let North Korean athletes participate in the Winter Olympic Games last month, though a meeting between Vice President Mike Pence and Kim’s sister, Kim Yo Jong, never materialized.