The United States and South Korea on Friday expressed "serious concern" about North Korea's first-use nuclear doctrine and warned that any nuclear attack would be met with an "overwhelming and decisive response."

In a joint statement following a bilateral dialogue on extended deterrence, which refers to the use of the U.S. nuclear arsenal to protect allies, the two countries said they had committed to using "all available levers," including diplomatic, military and economic tools, to counter North Korean threats.

They said a nuclear test by North Korea would elicit "a strong and resolute whole-of-government response."

The meeting attended by senior officials took place amid signs that North Korea may carry out its first nuclear test in years. The country's top legislature adopted a law earlier this month authorizing the launch of pre-emptive nuclear strikes, according to state media.

The United States and South Korea "expressed their serious concern over the DPRK's escalatory and destabilizing messaging related to nuclear weapons use, including its adoption of the new nuclear policy law," the statement said, using the acronym of the Democratic People's Republic of Korea, North Korea's official name.

The United States vowed to strengthen coordination with South Korea to "continue to deploy and exercise strategic assets in the region in a timely and effective manner," it said.

The two countries also highlighted combined training for F-35 fighter jets in July and the upcoming deployment of the U.S. aircraft carrier Ronald Reagan in the Indo-Pacific region as "a clear demonstration of such U.S. commitment." The carrier's home port is in Japan's Yokosuka, near Tokyo.

Both sides pledged to continue their cooperation to promote peace and stability in the Indo-Pacific, including through bilateral exercises and training as well as trilateral and multilateral cooperation with partners throughout the region.

South Korea's First Vice Foreign Minister Cho Hyun Dong and U.S. Undersecretary of State for Arms Control and International Security Affairs Bonnie Jenkins were among those who attended the meeting of the Extended Deterrence Strategy and Consultation Group.