A South Korean official Monday urged North Korea (search) to quickly respond to Washington's recent recognition of the country's sovereignty, saying it could lead to a turning point in the standoff over Pyongyang's nuclear programs.

Kim Sook, director-general of the foreign ministry's North American affairs bureau, said it was time for North Korea to give a "serious response" to issues discussed at the first meeting with U.S. officials in almost a year.

On Sunday, North Korea indicated a willingness to return to the nuclear bargaining table but said it "will continue to closely watch the U.S. side's attitude" to clarify what it called conflicting statements on American policy toward the reclusive state.

Kim said the North should be ready to respond to the May 13 meeting in New York, during which U.S. officials explained their position on nuclear nonproliferation within the context of stalled six-nation talks on North Korea's nuclear weapons programs.

"We don't think there is any reason (for North Korea) to continue to closely watch," Kim told KBS Radio. "How North Korea will respond will become a watershed in the resolution of the North Korean nuclear issue."

Kim did not elaborate.

The comments came as concerns mount that Pyongyang is moving toward extracting weapons-grade plutonium and could be preparing for a nuclear test.

There has been a flurry of efforts to get North Korea back to negotiations following its announcement two weeks ago it had removed 8,000 fuel rods from a reactor, a step toward extracting weapons-grade plutonium.

Expressing a sense of urgency, Russia's military chief of staff called for steps to prevent the North from conducting nuclear tests.

"Today it is necessary to do everything possible in order not to allow North Korea to conduct (nuclear) tests," Gen. Yuri Baluyevsky, chief of the general staff of the armed forces, said in televised comments. He did not specify what might be done to prevent it.

Baluyevsky, who spoke during a meeting with his Japanese counterpart, Gen. Hajime Massaki, also called for the renewal of six-nation talks, which stalled in June. The talks involve the two Koreas, the United States, Russia, Japan and China.

"We simply must not allow the testing or existence of nuclear weapons on the Korean peninsula," Baluyevsky said.

Russian Foreign Minister Sergey Lavrov told Japan's Kyodo News agency that the solution to the crisis "must lie in negotiations and not in a race to build up arms, especially nuclear ones."

A North Korean Foreign Ministry spokesman was quoted as saying Sunday that Pyongyang "will continue to closely watch the U.S. side's attitude, and when the time comes we will officially deliver to the U.S. side our position through the New York contacts."

The spokesman reaffirmed North Korea's commitment "to peacefully resolve the issue through dialogue and negotiations," according to the North's official Korean Central News Agency.

North Korea, with a history of using brinksmanship to wring aid from the West, claimed in February it had nuclear weapons and said it would indefinitely boycott arms talks until Washington drops its "hostile" policy.

The North's nuclear claim has not been verified, but U.S. intelligence and other estimates say it has as many as six atomic weapons.

The spokesman also said U.S. officials reaffirmed recognition of the North's sovereignty at the May 13 meeting at the United Nations and said Washington would not attack the reclusive nation. But the spokesman complained that some U.S. administration officials were still making remarks that "threaten" his country.

Secretary of State Condoleezza Rice (search) said earlier this month that "the United States, of course, recognizes that North Korea is sovereign." But Washington's chief envoy on North Korea, Christopher Hill, said during a visit to Seoul last week that a nuclear test by Pyongyang would provoke unspecified action.

The two Koreas were to meet Tuesday at the North Korean border town of Kaesong to work out details of a South Korean delegation's trip to attend a Pyongyang festival marking the 5th anniversary of the June 15 Korea summit accord.