SEOUL — South Korea and the U.S. are watching for signs of a third nuclear test in North Korea.

“This test could happen at any time without warning,” a U.S. Forces Korea statement said Thursday.

“The U.S. and Republic of Korea alliance is strong, and we continue to work closely together to maintain security on the peninsula. A North Korean nuclear test would be a highly provocative act and a significant violation of United Nations Security Council resolutions,” the statement said.

A spokesman for South Korea’s Ministry of National Defense said the country has formed a crisis management task force to monitor for a possible test, which Pyongyang claims it will conduct in retaliation for U.N. sanctions levied against the communist nation for launching a rocket in December.

North Korea conducted nuclear tests in 2006 and 2009, and, to the international community’s frustration, appears to have continued with its nuclear development program despite condemnation and economic sanctions. Pyongyang claimed the Dec. 12 launch put a peaceful satellite into orbit, but it was widely believed to be a test of technology that could one day allow it to strike the continental U.S. with a nuclear warhead.

South Korean officials have suggested that they could respond to another nuclear test with stronger measures.

“If North Korea misjudges the situation and pushes ahead with a provocation again, it will cause very grave consequences,” Park Jeong-ha, a spokesman for South Korean President Lee Myung-bak, said Wednesday, without providing specifics, according to Yonhap News.

USFK commander Gen. James Thurman said last week he is worried about another North Korea provocation and that U.S. forces are “highly vulnerable” following the recent rocket launch.

Senior U.S. and South Korean military officials are also discussing the matter with their Japanese counterparts, the MND said.

rowlanda@pstripes.osd.milchang.yookyong@pstripes.osd.mil