Government officials from the three nations have been coordinating to hold Trilateral Coordination and Oversight Group (TCOG) talks at the earliest opportunity after the Japan-South Korea summit meeting scheduled for June 7.

"With a summit meeting between Japan and South Korea, the ring (of three nations) will be completed," Vice Foreign Minister Yukio Takeuchi said.

The United States held separate summit talks with South Korea and Japan earlier this month.

At a TCOG meeting, working-level officials from the three nations are expected to coordinate each nation's position on North Korea and discuss in detail measures to deal with North Korea's nuclear weapons development, the sources said.

By holding such talks, the three nations intend to demonstrate their strong commitment to trilateral relations and to containing North Korea's attempts to drive a wedge among them, according to a senior Foreign Ministry official. Japan considers that keeping South Korea on the Japan-US side is essential to keep Pyongyang in check.

Japan and the United States agreed at a summit meeting last week to take tougher measures if North Korea escalated its nuclear activities.

However, South Korea and the United States at an earlier summit meeting agreed merely to consider further steps to be taken on North Korea.