Chief nuclear negotiators of South Korea, the United States and Japan met Thursday in Tokyo to discuss the stalled nuclear negotiations with North Korea.

A senior official in Seoul said Thursday it’s crucial to resume the six-party talks as soon as possible to maintain the momentum gained during Japan’s recent talks with North Korea.

The official said negotiators from South Korea and Japan held intensive discussions the previous day on various issues. Topping the agenda were North Korea’s nuclear declaration, the verification of its nuclear disablement efforts, as well as corresponding energy aid for the North.

After the three-way meeting, U.S. chief negotiator Christopher Hill plans to visit China to discuss the resumption of the nuclear dialogue and the North Korean declaration.