"Mr Kelly noted that the inter-Korea talks play the underpinning role in the effort to resolve the North Korean nuclear programs," a senior Unification Ministry official, Park Chan-bong, told Reuters.

Unification Minister Jeong Se-hyun hosts a North Korean delegation for talks beginning on Tuesday in Seoul.

For four days, the focus of the effort to bring North Korea to the negotiating table shifts away from diplomats to the highest-running channel of dialogue between the two Koreas.

Jeong's ministry pursues economic and humanitarian cooperation with the North under Seoul's policy of rapprochement with its communist neighbor, which is aimed at softening a half-century of ideological and military tension on the peninsula.

Foreign Minister Ban Ki-moon echoed mounting optimism that the six countries - which also include China, Japan and Russia - will be able to meet soon.

"It is our position to use this ministerial meeting between the South and the North to have more intensive discussions in a way conducive to a successful second round of meetings," he said in comments as he met Kelly.

Ban urged more consultations between South Korea, Japan and the United States "again when the dates are set."

Kelly said on arrival in Seoul on Sunday he was "mildly optimistic" that the six-way talks might resume before very long, perhaps even this month.

South Korea, Japan and the United States recently abandoned efforts to draft a statement going into the talks on how Washington and Pyongyang would begin closing their differences.

Washington seeks a complete end to the North's nuclear programs, while Pyongyang is demanding assurances that the United States will forswear military action against the North.