"Actions are more important than words," Unification Ministry spokesman Kim Hyung-Seok said of the offer contained in a letter delivered Friday by an envoy of North Korean leader Kim Jong-Un to Chinese President Xi Jinping.
Chinese state media said the letter cited the North's willingness to resume stalled six-party talks on denuclearisation involving China, the two Koreas, the United States, Russia and Japan.
The reported message was greeted with scepticism in South Korea, where observers saw it as an effort to appease Beijing, rather than a genuine signal of intent.
Seoul and Washington, meanwhile, insist that the North must demonstrate its commitment to abandoning its nuclear weapons programme in order for formal talks to begin.
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The North Korean state media's coverage of envoy Choe Ryong-Hae's visit to China made no mention whatsoever of a dialogue proposal.
Of the letter handed to President Xi, Pyongyang's official Korean Central News Agency (KCNA) said only that it conveyed Kim's desire to deepen the "traditional friendship" between North Korea and China.
China is North Korea's key economic benefactor and diplomatic protector, but it signed off on UN sanctions punishing Pyongyang for its nuclear test in February.
"If the North genuinely wants dialogue, the first step should be responding to our repeated call for working-level governmental talks on the Kaesong industrial complex," the spokesman said.
Kaesong was the most high-profile victim of two months of elevated military tensions that followed the North's nuclear test.
Established just north of the border in 2004 as a rare symbol of cooperation, the showpiece project had more than 120 South Korean firms employing some 53,000 North Korean workers.