SEOUL, South Korea (AP) — South Korea’s president called on North Korea to stop raising animosities and return to talks, saying Monday the rivals must not reverse the peace deals that he and North Korean leader Kim Jong Un reached during 2018 summits.

President Moon Jae-in’s efforts to defuse rising animosities came after North Korea threatened Friday to destroy an inter-Korean liaison office located in North Korea and take unspecified military steps against South Korea.

If North Korean were to take such actions it would be a serious setback to Moon’s efforts toward Korean reconciliation and finding a negotiated solution to the North Korean nuclear issue.

“North Korea must not sever communications and create tensions to turn back the clock to a past confrontational period,” Moon said during a meeting with top presidential advisers, according to his office. “We must not push back the pledges of peace that Chairman Kim Jong Un and I made."

Moon, a liberal who met Kim three times in 2018, was a driving force behind now-dormant diplomatic efforts between Pyongyang and Washington, including the summit between Kim and President Donald Trump in Singapore in 2018.

During two of the three inter-Korean summits, Moon and Kim agreed to achieve denuclearization of the Korean Peninsula and take other steps to boost exchanges and dial down military tensions. Those summits initially helped to improve their countries' ties significantly, before their relations became strained again after the breakdown of a second Kim-Trump summit in Vietnam in early 2019.

North Korea has recently unleashed a slew of harsh rhetoric against South Korea, accusing it of failing to prevent activists from launching propaganda leaflets across their border. In an apparent bid to soothe North Korea, Moon’s government vowed to ban civilian leafleting campaign. North Korea has said the South Korean response lacks sincerity.

Some observers say North Korea is frustrated because Seoul has failed to break away from Washington and revive stalled joint economic projects held back by U.S.-led sanctions. They also speculate North Korea initially thought Moon would help it win badly needed sanctions relief but got upset after Kim returned home empty handed from the 2019 summit with Trump.

Moon said the two Koreas must take the initiative in finding a breakthrough, calling the nations “the masters of the destiny for the Korean Peninsula.” He said his government will keep striving to promote dialogue with North Korea.

Monday marks the 20th anniversary of the first-ever inter-Korean summit — between Kim’s late father Kim Jong Il and South Korea's then-President Kim Dae-jung in Pyongyang.

The Koreas remain split along the world’s most heavily fortified border since they were divided into a U.S.-backed South Korea and a Soviet-controlled North Korea at the end of the World War II in 1945.