"It is time for North Korea to respond as 10 days have passed since the US-North Korean contract in New York," Kim Sook, head of the North American affairs bureau at the South's foreign ministry, told state-run KBS radio.

"(North Korea) has no reason to continue waiting, and it must make a prudent and sincere reply."

The North acknowledged Sunday a rare meeting on May 13 with the United States and announced it would contact Washington when the time was right to update its position on the nuclear stand off.

At the New York meeting, Washington reaffirmed its recognition of North Korea as a sovereign state and repeated that it had no intention to invade the Stalinist country, an unidentified North Korean foreign ministry spokesman said.

The May 13 meeting at the North's UN representative office, the first face-to-face US-North Korean contact in half a year, came as Washington tries to revive six-nation talks which have been stalled for 11 months.

The North has boycotted the talks since the third round in June last year. Aside from the United States and North Korea, the talks include host China, Russia, Japan and South Korea.

After declaring itself nuclear-armed in February, North Korea said this month it had unloaded 8,000 spent fuel rods from its reactor, a step that would allow it to reprocess weapons-grade plutonium for more nuclear bombs.

US officials have also said recently there were signs the North is preparing for a nuclear test.

Former South Korean president and Nobel Peace Prize laureate Kim Dae-Jung on Monday also urged Pyongyang to return to the six-party talks.

Speaking in Tokyo, Kim said North Korea is "scared" and wants better ties with Washington.

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