The United States is "stepping up cooperation" with Japan and South Korea over negotiations to realize denuclearization on the Korean peninsula, U.S. Assistant Secretary of State Christopher Hill said in Washington on Monday.

Hill, top U.S. nuclear negotiator, made the remarks after his meeting with his counterparts Kim Sook of South Korea and Akitaka Saiki of Japan.

"We're really stepping up our cooperation not only bilaterally but trilaterally. We have a lot to discuss here. We'll work out our work plan ahead," Hill told reporters without giving any details.

Hill's talks with Kim and Saiki focused on how to verify North Korea's declaration and the possibility of a next round of disarmament talks, State Department spokesman Sean McCormack said earlier in the day.

The latest meetings occurred when North Korea delivered on May 8 the United States more than 18,000 pages of its sensitive nuclear records, and the six-party talks on the nuclear issues on the Korean Peninsula was reportedly to be resumed before June 15 after an eight-month suspension.

(Xinhua News Agency May 20, 2008)