1148 GMT January 26, 2020
The leader of the North met with Moon three times this year – twice at the border truce village of Panmunjom and once in the North's capital Pyongyang – as a reconciliatory push gathered pace, AFP wrote.
During Moon's visit to Pyongyang in September, Kim promised to pay a return visit to the South's capital Seoul "at an earliest date," sparking speculation he may visit by the end of this year.
But the much-anticipated trip has not yet materialized, which left the young leader feeling "much regret," according to Kim's letter sent to mark the end of the year, Moon's spokesman said.
The North's leader "expressed a strong determination to visit Seoul while watching future situation," Kim Eui-kyeom told reporters.
Kim also "expressed an intention to meet with Moon frequently in 2019" to pursue peace and "solve the issue of denuclearizing the peninsula together," the spokesman said.
Moon welcomed the latest message, saying Kim had also expressed "active intention to carry out agreements" made in his previous summits with the US and the South.
The two neighbors technically remain at war after the 1950-53 Korean War ended with a cease-fire instead of a peace treaty.
Moon – a dovish former human rights lawyer – has advocated talks to push the nuclear-armed North toward denuclearization.
Cross-border ties improved markedly in 2018 as Kim made a series of reconciliatory gestures – including a historic summit with US President Donald Trump in June in Singapore.
But progress in pushing the North to give up its atomic arsenal has stalled as Washington and Pyongyang accuse each other of dragging their feet and acting in bad faith.