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 strategic cooperation with ‘anti-imperialist’ countries, according to the Korean Central News Agency (KCNA).He said the security situation on the Korean Peninsula has become extremely dangerous due to what he claims are ‘unprecedented’ US-led confrontational moves against North Korea.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. (QNA)