SEOUL (Reuters) - North Korea rejected an invitation for leader Kim Jong Un to attend a planned summit in South Korea next week with Southeast Asian nations, saying it would be “pointless” due to strained ties with Seoul, North Korean state media reported on Thursday.

FILE PHOTO: South Korean President Moon Jae-in and North Korean leader Kim Jong Un walk during a luncheon, in this photo released by North Korea's Korean Central News Agency (KCNA) on September 21, 2018. KCNA via REUTERS/File Photo

South Korean President Moon Jae-in sent a letter of invitation to Kim on Nov. 5, with an offer for an envoy to attend if he was unable to participate, the official KCNA news agency said.

Moon has said Kim might join when he hosts leaders of the Association of Southeast Asian Nations (ASEAN) in the South Korean port city of Busan next week to celebrate the 30th anniversary of their partnership.

Moon’s office said it was “very regretful” Kim would miss the event, and the invitation was meant to rally international support for the two leaders’ joint efforts to foster peace.

While thanking Seoul for the invitation, North Korea requested the South’s “understanding that we failed to find out the proper reason” for Kim to participate, KCNA said.

The statement accused South Korea of failing to implement agreements from past summits between Kim and Moon by depending on the United States.

“As nothing was achieved in implementing the agreements ... the north-south summit for the mere form’s sake would be pointless,” KCNA said.

“Not content with sustaining losses from dependence on the United States, the south side made an offer for discussing the north-south relations in the theatre of multi-lateral co-operation. This makes us only dubious.”

The two Koreas undertook a flurry of diplomacy including three summits last year, during which Moon and Kim agreed to improve ties and restart stalled business initiatives.

But there has been no significant progress amid tightening sanctions aimed at the North’s nuclear and missile programmes, and stalled denuclearisation talks after Kim’s failed second summit with U.S. President Donald Trump.

Pyongyang has stepped up criticism against Seoul and Washington in recent months for their joint military drills and the South’s purchase of U.S. weapons designed to fend off North Korean threats.

“North Korea now considers summits without payment for co-operation as empty diplomacy that merely helps Moon and Trump raise domestic political support,” said Leif-Eric Easley, who teaches international studies at Ewha Womans University in Seoul.