"We could find a clue to resolving the problem if a North-South summit is held," the Nihon Keizai Shimbun quoted Lee as saying in an interview with the economic paper in Seoul conducted on Thursday.

He also said Seoul had already proposed holding such a meeting to Pyongyang, the paper said.

The move reflected Seoul's strategy of deepening understanding at a summit and making the North take a softer stance, it said.

If realised, the meeting would be the first inter-Korean summit since then South Korean president Kim Dae-Jung met North Korean leader Kim Jong-Il in June 2000 in Pyongyang.

Lee, who was in the South Korean delegation for the first summit, told the paper he had since been in contact with senior North Korean officials.

Lee was also quoted as saying "there has been an indirect request for a visit (by the South Korean leader) to the North."

"I think it is important to seek a clue to solving the North Korean nuclear issue," he told the paper, while adding the North Korean leader should come to South Korea this time round.

Six-nation talks, among the two Koreas, China, Japan, Russia and the United States, aimed to solve the issue are deadlocked.

"There are many difficult questions to resolve in order to reach a concrete conclusion at a fourth round of six-way talks," which are supposed to be held by the end of September, Lee was quoted as saying.

The prime minister also said "it is only a matter of time" that the North will revert to an open-door policy while warning against the risk the state "would collapse if it implements reform and liberalisation programme too fast."

He said Seoul was ready to give wide-ranging assistance to Pyongyang if it abandons its nuclear programmes.

The stand-off over the North's quest for nuclear weapons began in October 2002 when Washington accused it of operating a secret programme based on enriched uranium in breach of a 1994 accord on freezing its separate plutonium program.

Pyongyang has denied running the uranium-based program but has restarted its plutonium program.

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