At a key meeting of the ruling Workers' Party, Kim highlighted the need to boost the country's nuclear arsenal and secure "overwhelming military power" to defend its sovereignty and security.
Kim accused Washington and Seoul of carrying out a "plot to isolate and stifle" Pyongyang, calling it "unparalleled in human history."
The report came hours after North Korea fired a short-range ballistic missile off its east coast, in a rare late-night, New Year's Day weapons test.
The Japanese government has filed a diplomatic protest against North Korea after it launched a ballistic missile in the early hours of Sunday, Japan's Defence Minister told reporters in Tokyo.
"In the last year, North Korea's repeated missile launches have gravely raised tensions on the Korean peninsula and regionally. North Korea's series of provocations threatens the peace and security of Japan, the region, and the international community, and must not be tolerated," Defence Minister Yasukazu Hamada said.
The move came less than 24 hours after North Korea launched three ballistic missiles on Saturday, capping a year when the isolated country conducted an unprecedented number of missile tests.
The latest launch came as Pyongyang's ruling Workers' party held a key meeting, which leader Kim Jong Un had previously used to make major policy announcements for the new year.
Reuters