U.S. President Donald Trump has agreed to meet with North Korean leader Kim Jong Un by May, a South Korean official announced late on Thursday, claiming that Kim has committed to denuclearization and will refrain from any further nuclear or missile tests.

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South Korean National Security Adviser Chung Eui-yong, speaking outside the White House in Washington, D.C., said he had briefed President Trump about his recent visit to the North Korean capital, where he and other South Korean officials met with Kim for more than four hours.

“I told President Trump that in our meeting, North Korean leader Kim Jong Un said he’s committed to denuclearization. Kim pledged that North Korea will refrain from any further nuclear or missile tests,” Chung said. There was no immediate comment from North Korea to confirm South Korea’s claim.

VIDEO: South Korea announces details of meeting with Kim Jong Un

Chung added that Kim understood that joint military exercises between the United States and South Korea, which North Korea has long viewed as a threat, must continue. Kim further expressed his eagerness to meet with Trump “as soon as possible,” the official said.

“President Trump appreciated the briefing and said he would meet Kim Jong Un by May to achieve permanent denuclearization,” Chung told reporters. The White House confirmed that Trump had accepted Kim’s invitation, adding that the place and time has not yet been determined.

Chung said South Korea and the U.S. are “optimistic” about the possibility to test a peaceful resolution to North Korea’s nuclear weapons program. He added, however, that the international community must “not repeat the mistakes of the past” and urged that the pressure must continue until North Korea “matches its words with concrete actions.”

Tensions on the Korean Peninsula were high throughout much of 2017, fueled by North Korea’s frequent missile tests and its advancing nuclear weapons program, as well as U.S. military exercises and threatening statements by President Donald Trump.

The recent talks between North and South Korea have allowed tensions to ease, even though North Korea has publicly insisted that its nuclear weapons program is not up for discussion under any circumstance.

A South Korean delegation visited Pyongyang earlier this week and met with Kim, making them the first officials from the South to ever meet with him in person. Kim and South Korean President Moon Jae-in are due to meet for the first time in the second half of April.

Following Monday’s historic meeting with Kim, South Korea’s presidential office claimed that North Korea had indicated that it would have no reason to retain its nuclear weapons if it believes there is no longer a military threat and the regime’s safety is guaranteed. North Korea has neither confirmed nor denied South Korea’s statement.