North Korean leader Kim Jong-un has called for stepped-up efforts to prepare for war, saying the United States is engaged in "unprecedented" acts of confrontation against the country, state media reported Thursday.

In the second-day session of the plenary meeting of the ruling Workers' Party on Wednesday, Kim also presented a goal of strengthening cooperation with "anti-imperialist" countries, according to the Korean Central News Agency.

"He set forth the militant tasks for the People's Army and the munitions industry, nuclear weapons and civil defense sectors to further accelerate the war preparations," the KCNA said in an English-language dispatch.

He said the security situation on the Korean Peninsula has become unprecedentedly grave due to anti-North Korea confrontation moves by the US and its followers.

Kim also vowed to "expand and develop the relations of strategic cooperation with the anti-imperialist independent countries and dynamically wage the anti-imperialist joint action and struggle on an international scale," the KCNA said.

North Korea opened the year-end party meeting Tuesday to review state policies for this year and set those for 2024. Kim is expected to use the ongoing meeting as a venue to deliver his key speech to replace his annual New Year's Day address.

Experts said the North's leader is expected to issue a hostile message against the US and South Korea and lay out a set of measures to bolster its military capabilities, including a detailed plan to launch additional military spy satellites.

North Korea put a military spy satellite into orbit in November following its two previous failed attempts in May and August, respectively. (Yonhap)