U.S. Defense Secretary Leon Panetta and South Korean Minister of National Defense Kim Kwan Jin issued the declaration Wednesday after the 44th U.S.-Republic of Korea Security Consultative meeting, the Pentagon reported.
Panetta said the alliance between the countries "will remain a cornerstone of stability in Northeast Asia, adding they had reaffirmed that North Korean "aggression or military provocation will not be tolerated."
Kim noted that the recent change in North Korean leadership had created "increasingly unpredictable security situations."
During the meeting, the United States agreed to maintain its current level of U.S. forces in South Korea, which Kim said would strengthen military capabilities and readiness and provide "overwhelming reinforcement" in the event of North Korean military action.
The officials said the U.S. and South Korea would work to revise missile guidelines in a "tailored" manner to deal with any potential aggressive postures by the North.
Kim said the North has been preparing for a third nuclear test, "and when the time comes for a political decision, it may in fact resort to this third nuclear test."
Kim added, efforts should continue "to shape the environment" to get Pyongyang to return to the six-party nuclear talks.
Panetta said the United States was working with other counties in the region to "send a clear message" to the North to return to the talks.