Updated

South Korea (search) expressed deep concern Wednesday over North Korea's (search) possible moves to make more weapons-grade plutonium (search) and urged the communist country to return to international disarmament talks.

"The government is closely watching activities at the North's Yongbyon nuclear reactor, and we cannot but express serious concern should the North move toward reprocessing," Foreign Minister Ban Ki-moon told reporters. "Such activity is not in the interest of the North or the international community."

North Korea's 5-megawatt reactor at Yongbyon was reloaded with a fresh batch of 8,000 fuel rods in early 2003, after international inspectors were expelled following a breakdown of a 1994 U.S.-North Korean agreement on halting Pyongyang's nuclear weapons development.

The South Korean government confirmed Monday that the North has suspended work at the reactor — a move that could allow the removal of spent fuel rods for reprocessing to extract weapons-grade plutonium.

International talks to convince the North to abandon its nuclear ambitions — including China, Japan, Russia, South Korea and the United States — have been suspended since last June. Pyongyang further decreased prospects for a resolution after announcing Feb. 10 that it possessed nuclear weapons and would indefinitely boycott the negotiations.

North Korea has also since demanded the United States recognize it as an equal dialogue partner and apologize for U.S. Secretary of State Condoleezza Rice labeling the North one of the world's "outposts of tyranny."

On Wednesday, Ban again downplayed comments by senior U.S. officials about the possibility of referring the North's nuclear activities to the U.N. Security Council, saying that would be a last resort to be taken only when current diplomatic efforts fail.

"There have been no discussion between South Korea and the United States on this," he said, adding that countries to the six-party talks were still talking about bringing the North back to the negotiating table.

In the continuing diplomacy over the standoff, South Korean Defense Minister Yoon Kwang-ung departed Wednesday for a trip to Russia, where he will meet with his counterpart there to discuss the North Korea issue and other concerns.