Obama says Sony hack was not 'an act of war'

Obama's Republican critics have accused North Korea of waging "cyber warfare" by targeting Sony, urging the president to respond robustly to the crisis.

Obama, however, said that while his administration was planning a "proportionate" response, the hack of Sony was an act of "cyber vandalism" rather than war.

"I don't think it was an act of war. I think it was an act of cyber vandalism that was very costly, very expensive. We take it very seriously," Obama told CNN.

Obama did not elaborate on what action the US government may take but said Washington could review whether or not to put North Korea back onto its list of state sponsors of terrorism.

North Korea was removed from the US list in 2008 as part of negotiations over the nation's nuclear program.

Obama, in the pre-taped interview on CNN's "State of the Union," emphasized however that any change in that status could only happen after a careful evaluation of the facts.

"We've got very clear criteria as to what it means for a state to sponsor terrorism. And we don't make those judgments just based on the news of the day," Obama said.

"We look systematically at what's been done and based on those facts, we'll make those determinations in the future," he added.

Obama faced fresh calls from Republican critics on Sunday to target North Korea with stiff sanctions.

"It's more than vandalism, it's a new form of warfare that we're involved in and we need to react and react vigorously, including reimposing sanctions," said US Senator John McCain, the incoming chairman of the Senate Armed Services Committee.

Washington accuses Pyongyang of being behind the hack at Sony that led to the release of embarrassing emails and caused executives to halt the debut of the madcap comedy action film "The Interview."

The film about a fictional CIA plot to kill the country's leader infuriated North Korea, although Pyongyang has repeatedly denied it was behind the cyber-assault on Sony.

North Korea on Saturday called for a joint probe into the investigation with the United States into the hacking -- an offer swiftly rebuffed by security officials in Washington.

North Korea threatened Sunday to hit back at the White House and other US targets if it was sanctioned over the alleged hacking.

The North's National Defense Commission, in a statement on the official news agency, said its army and people "are fully ready to stand in confrontation with the US in all war spaces including cyber warfare space to blow up those citadels,"

"Our toughest counteraction will be boldly taken against the White House, the Pentagon and the whole US mainland, the cesspool of terrorism, by far surpassing the 'symmetric counteraction' declared by Obama," it said.

The North, which has in the past made statements threatening the US mainland, accused the Obama administration of being "deeply involved" in the making of the "The Interview" at the center of the Sony hacking.

It again praised the "righteous action" by the hacking group, which has styled itself Guardians of Peace, but said it was unaware where they were based.

The FBI has cited "significant overlap" between the attack and other "malicious cyber-activity" with direct links to Pyongyang, including an attack on South Korean banks blamed on the North.

The North said in Sunday's statement it has never attempted or made a cyber-attack on South Korea.