There is a "desperate need" for practical ways to improve ties with North Korea, South Korea's President Moon Jae-in said on Tuesday, adding that he was ready to meet the country's reclusive leader in Pyongyang, repeatedly if necessary.

Moon, sidelined from his leading role in the diplomatic effort with the in 2018, said he regretted the past year's lack of progress in negotiations.

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In an annual New Year's speech in Seoul, Moon called for new talks with Kim Jong Un, and promised to keep up work to facilitate communication between North Korea and the US.

"In a time of deadlock in US-North Korea talks - and where we are even concerned about a step backward in inter-Korean relations - we are in desperate need of practical ways to improve inter-Korean cooperation," he said.

"I'm willing to meet repeatedly and talk ceaselessly" with the North, Moon said in his speech, which was broadcast live.

He also said South Korea would continue to push for reopening the Kaesong Industrial Complex, tours to Mount Kumgang, and border cooperation without elaborating. He added the joint 2032 Olympics bid would be a unifying event, as would completing the inter-Korean railway.

North Korea has not responded to recent overtures from the government in Seoul, and cooperation projects between the neighbours have stalled in the face of international sanctions.

Pyongyang has expressed frustration at what it calls Washington's lack of flexibility, while US officials say the country must take more concrete steps to dismantle its nuclear weapons and ballistic missile programmes before sanctions can be eased.

"The momentum for US-North Korea talks must continue," Moon said. "Provocations and threats are not helpful for anyone."

Over the New Year, Kim said he planned to further develop nuclear programmes and introduce a "new strategic weapon" in the near future, although he signalled there was still room for dialogue with the US.

Security and prosperity on the Korean Peninsula are dependent on resolving international tensions, but the two Koreas could achieve progress through cooperation, Moon said.

"I suggest South and North Korea put our heads together," he said.