This image, provided by the North Korea's Central News Agency on Dec. 29, shows North Korean leader Kim Jong-un speaking at a party meeting. Yonhap

North Korea has declared its strongest response strategy toward the United States during a year-end plenary party meeting, asserting that the military cooperation among South Korea, the U.S., and Japan is evolving into an invasive nuclear military bloc, state media reported Sunday.

The strategy was adopted during the annual year-end general meeting of the Central Committee of the Workers' Party of Korea, held from Monday to Friday and presided over by North Korean leader Kim Jong-un, the Korean Central News Agency (KCNA) said.

The U.S. is the "most reactionary" state, unwaveringly adhering to anti-communism as its national policy, the KCNA reported, adding that "the strongest response strategy toward the U.S." was declared in the interest of national security.

It also accused the military cooperation among Seoul, Washington and Tokyo of expanding into an invasive nuclear military bloc.

During the meeting, Kim ordered the refinement of warfare tactics to meet the demands of modern warfare and the shifting war attempts by "enemies," while also calling for continued improvement in the warfare capacities of the army, the KCNA also said.

During the session, Pak Thae-song, a party secretary, was appointed premier, replacing his predecessor Kim Tok-hun. (Yonhap)