North Korea's Kim offers rare praise for South's departing Moon

North Korean leader Kim Jong Un has thanked South Korea's outgoing president for trying to improve relations, a rare gesture of goodwill but one that analysts said may not be enough to head off growing tension between the two Koreas.

The warm words from North Korea to President Moon Jae-in came in an exchange of letters less than three weeks before Moon leaves office to be replaced by a conservative leader who has already signalled a tougher line on North Korea. 

Analysts were sceptical that North Korea's message heralded a broader improvement in relations, and warned that the praise for Moon could be a bid to portray his successor, Yoon Suk-yeol, as responsible for any further deterioration in ties.

North Korean state media was the first to report the exchange and the unexpected North Korean plaudits for the stalled effort by Moon and his liberal administration to engage.

"Kim Jong Un appreciated the pains and effort taken by Moon Jae-in for the great cause of the nation until the last days of his term of office," North Korea's KCNA state news agency reported.

The exchange of letters was an "expression of their deep trust", it said.

The letters come against a backdrop of tension since a failed North Korea-US summit in 2019, exacerbated last month when North Korea launched intercontinental ballistic missiles (ICBM), ending a self-imposed 2017 moratorium.

Moon sent a letter on Wednesday and promised to try to lay a foundation for unification based on joint declarations reached at summits in 2018, despite the "difficult situation", KCNA said.

Moon's office confirmed that he had exchanged "letters of friendship" with Kim.

Moon said the "era of confrontation" should be overcome with dialogue, and inter-Korean engagement was now a task for the next administration, his spokeswoman told a briefing. Moon also expressed hope for the swift resumption of US-North Korea denuclearisation talks.

Read  North Korea ballistic 'monster missile' explodes after launch

Kim said in his reply on Thursday that their "historic" summits gave the people "hope for the future", and the two agreed that ties would develop if both sides "make tireless efforts with hope", KCNA reported.

The exchange came as US Special Representative for North Korea Sung Kim was in South Korea for talks. The US envoy has said he is open to sitting down with the North at any time without preconditions, but it was unclear whether Moon's letter specifically proposed a meeting.

Analysts questioned the North's true intentions.

"This looks more like another step in building the pretext to blame Yoon for more escalation from North Korea, rather than an olive branch to Yoon or Biden," said Markus Garlauskas, a senior fellow with the Atlantic Council think tank and former US national intelligence officer for North Korea.

Yang Moo-jin, a professor at the University of North Korean Studies in Seoul, said the letters could signal to Yoon that the door for cooperation was still open, and a potential seventh nuclear test by the North or any other future action would hinge on Yoon's approach.

Yoon, who takes office on May 10, has said that he is open to dialogue but greater military deterrence and a stronger US alliance are needed to counter the North's "provocations".

Kwon Young-se, Yoon's nominee to oversee cross-border affairs, said the exchange of letters was a "good thing" and Kim offered "positive" views on inter-Korean ties.

"There was some content that the new government would want to hear," he told reporters. "It was very positive that he does not negatively see trust and progress in relations."

Tension escalated when North Korea last month conducted its first full ICBM test since 2017, and there are concerns that it is preparing to restart nuclear testing.

Moon staked his legacy on improving inter-Korean ties and helped arrange unprecedented meetings between Kim Jong Un and then US President Donald Trump in 2018 and 2019.

Three summits Kim and Moon held in 2018 promised peace and reconciliation but relations have soured, with the North warning of destructive action and demolishing facilities built by South Korean firms for joint projects. 

In 2020, the North spectacularly blew up a joint liaison office on the border, which Moon's government had spent 9.78 billion won ($8.6 million) renovating.

The two leaders tried again to mend ties last year but little progress was made and Pyongyang then criticised Seoul's "double standards" over weapons. 

North Korea's statement left open a possibility for Moon to play a role as envoy, but Christopher Green, a Korea specialist at Leiden University in the Netherlands, said it was unlikely to have a positive impact on his reputation.

The statement could stir controversy in the South by portraying Moon as "a deluded peacenik who, after all the weapons tests North Korea has conducted in the last eight months, is still writing convivial letters to Kim", Green said.