Former President Kim Dae-jung was a special guest speaker at the forum marking his landmark summit talks with North Korean leader Kim Jong-il four years ago.

The former president called on the North Korean leader to keep his promise to visit Seoul made during their historic summit.

The former president said South Koreans would warmly welcome the North Korean leader's visit to Seoul and like to see the leaders of the two Koreas discuss their mutual cooperation, prosperity and eventual reunification in another round of summit talks.

Kim also urged Pyongyang to give up nuclear ambitions while calling for Washington to offer security guarantees and improve ties with Pyongyang.

Meanwhile, former U.S. Ambassador to Seoul, Donald Gregg, threw his voice to Kim's idea by calling for direct talks between Washington and Pyongyang to defuse the nuclear standoff.

Gregg said the longer the U.S. refuses to enter into direct negotiations, the higher the price would become for transition into a new era while increasing the dangerous prospect of North Korea becoming a permanent nuclear power.