In the 1990s, North Korea planned attacks within the U.S. and even dispatched covert commando teams to the states in preparation for a strike should war break out between the two countries, according to declassified reports.

U.S. officials were aware of at least five covert commando teams that had been dispatched to America in the 1990s, according to a 2004 Defense Intelligence Agency report recently obtained by the Washington Free Beacon.

Should war break out between the U.S. and North Korea, the teams were trained and instructed to attack nuclear power plants and other targets in major cities, the heavily redacted report revealed.

The primary North Korean intelligence and special operations organization, the Reconnaissance Bureau, "had agents in place with missions to attack American nuclear power plants in the United States in the event of hostilities between the United States and the DPRK," the heavily redacted report says.

"The North Korean Ministry of People's Armed Forces established five liaison offices in early 1990s to train and infiltrate operatives into the United States to attack nuclear power plants and major cities in case of hostilities," the report reads. "One of the driving forces behind the establishment of the units and infiltration of operatives was the slow progress in developing a multi-stage ballistic missile."

North Korea said in a statement on Sunday that President Barack Obama was "recklessly" spreading rumors of its involvement in the cyberattack of Sony Pictures, and warned of strikes against the White House, Pentagon and the entire U.S. mainland.

The statement claimed that North Korea was not responsible for the attacks on the "ill-famed cesspool of injustice," but said whoever was responsible was justified in doing so, BBC reported.

"The army and people of the DPRK [North Korea] are fully ready to stand in confrontation with the US in all war spaces including cyber warfare space," the statement said.