Uri Party Chairman Moon Hee-Sang, on a visit to Tokyo, said that the three countries, which are part of the six-way talks on the North's nuclear program, each were playing supporting roles to persuade North Korea.

"We have strategies to deal with Pyongyang which can only happen when there is a strong relationship among South Korea, Japan and the US," he told a news conference.

"Seoul is playing the role of bringing Pyongyang to the table of the international community," Moon said.

South Korea has pursued a "sunshine policy" with its estranged neighbor, calling for engagement and aid to bring it into the international community. The United States and Japan have been skeptical of aid without guarantees that Pyongyang will make good on its promises.

A top Japanese diplomat expressed regret in May after offending South Korea by saying privately that Washington no longer trusted Seoul over North Korea.

Relations have also been strained over Japanese Prime Minister Junichiro Koizumi's visits to Yasukuni shrine, which honors war criminals among other war dead. Japan occupied Korea from 1910 to 1945.

Moon said the issue should not hinder ties between the two countries from developing.

"I have no intention to intervene in Japan's internal affairs," he said. "But I'd have to say if someone asks my opinion that I don't want Prime Minister Koizumi to visit the shrine."