The US White House said on Saturday it stood by the conclusion of the Federal Bureau of Investigation (FBI) that North Korea was to blame for a hacking attack that led Sony Pictures to cancel its release of the movie "The Interview," a comedy about a plot to assassinate the country's leader, Kim Jong Un.
"The government of North Korea has a long history of denying responsibility for destructive and provocative actions," National Security Council spokesman Mark Stroh said.
"If the North Korean government wants to help, they can admit their culpability and compensate Sony for the damages this attack caused," he added.
His remarks came after North Korea called the US accusations "groundless slander," proposing a joint investigation with the US into the cyber-attack, which resulted in the disclosure of a huge quantity of internal Sony data, including unreleased films, personal information on employees and executive emails.
Sony canceled the release of the movie, scheduled for Christmas Day, after hackers threatened cinemas that were planning to screen the premiere.
The unidentified spokesman for Pyongyang's Foreign Ministry, who on Saturday suggested the joint probe, also said his country knew how to prove it was not involved, and accused the US of lacking any specific evidence linking the attack with North Korea.
He also threatened "serious consequences" if the US did not accept the North Korean proposal.
The FBI said on Friday that analysis of the malware and internet infrastructure used in the hacking attack showed a "significant overlap" with "other malicious cyber activity" previously linked with North Korea, but gave little more detail on how it reached its conclusion.
On Friday, US President Barack Obama criticized Sony executives for giving in to the hackers' threats, saying that it was tantamount to a form of censorship that set a dangerous precedent.
Obama also pledged a "proportional and appropriate"response to North Korea over the attack, but did not go into details.
North Korea and the US are technically still at war after the 1950-53 Korean War ended with an armistice rather than a peace treaty, and the North has been subject to more than 50 years of US sanctions. The two states are also at loggerheads over Pyongyang's nuclear and missile programs.
In a separate statement on Saturday, North Korea said it would boost its "nuclear power" in response to what it called Washington's hostility, claiming that the US was planning to invade North Korea under the pretext that it was putting an end to human rights abuses there.
tj/jm (dpa, AP, Reuters)