Japanese Prime Minister Junichiro Koizumi and South Korean President Roh Moo-hyun pledged on Wednesday to extend aid to North Korea once communist Pyongyang halted its nuclear arms programmes.
The two key US allies in Asia agreed to speed up efforts to resolve a 20-month-old crisis over North Korea's nuclear ambitions, building on signs of progress in recent talks.
"If the North Korean nuclear problem is resolved, we made clear that South Korea and Japan will co-operate," Roh told a news conference, flanked by Koizumi after their summit on the South Korean resort island of Cheju.
"My country will carry out detailed and comprehensive economic co-operation projects with the North, and Japan will actively pursue diplomatic relations and economic co-operation with the North," he said.
Koizumi's two-day visit comes amid signs the United States is moving closer to the approaches of Japan and South Korea on how to break the impasse with North Korea.
Unlike Washington, both Tokyo and Seoul are conducting bilateral talks with Pyongyang. But South Korea and Japan both cite the nuclear dispute as a major impediment in efforts to normalise relations with the reclusive North.
Roh told reporters that he saw a glimmer of progress in last month's six-party talks involving the two Koreas, Japan, the United States, China and Russia.
"I believe that the last round of six party talks made progress that is worthy of considerable interest," Roh said.