Lindsay Deutsch

USA TODAY Network

North Korea is proposing a joint investigation with the U.S. to look into the massive cyberattack against Sony Pictures Entertainment.

On Saturday, a spokesman for North Korea's Foreign Ministry in Pyongyang promised "grave consequences" if the U.S. does not agree to a joint investigation.

"The U.S. should bear in mind that it will face serious consequences in case it rejects our proposal for joint investigation and presses for what it called countermeasures while finding fault" with North Korea, the spokesman said in a statement delivered by the Korean Central News Agency.

The statement also said the country knows how to prove it is not responsible for the hacking "without resorting to torture, as what the CIA does."

White House National Security Council Spokesman Mark Stroh said Saturday that the U.S. stands behind the FBI's conclusion the reclusive nation was responsible for the attack.

"The government of North Korea has a long history of denying responsibility for destructive and provocative actions," Stroh said. "If the North Korean government wants to help, they can admit their culpability and compensate Sony for the damages this attack caused."

The Sony hacking began Nov. 24 and has resulted in the massive release of Sony's internal e-mails and documents. Almost 38 million files were stolen.

The situation escalated on Dec. 16 when the hackers posted a message threatening 9/11-type attacks on theaters screening The Interview, the Seth Rogen-James Franco comedy that has been the apparent catalyst for the hackings. In the movie, the comedians play TV journalists commissioned to assassinate North Korean leader Kim Jong Un.

The hackers' threats led to several major movie theater companies announcing they would no longer screen The Interview.

Sony pulled The Interview's Dec. 25 wide release on Dec. 17, a decision that Obama disparaged in a conference Friday, saying, "I wish they had spoken to me first. ... I would have told them do not get into a pattern in which you're intimidated by these kinds of criminal attacks."

According to Reuters, North Korea state media has called the FBI's assertion that the country was behind the attack "slander."

Contributing: Associated Press