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Washington (CNN) - U.S. government officials are preparing to publicly blame North Korea for the Sony Pictures hack - but haven't yet decided how to respond to the attack.
The White House and other agencies are holding a series of high-level meetings to discuss the United States' range of options, a senior official in President Barack Obama's administration said.
"We do think it's appropriate to respond," the official said.
Those options could include new sanctions against North Korea, another source said.
White House press secretary Josh Earnest wouldn't confirm that the Obama administration has pinned the hack on North Korea, saying it's still being investigated by the FBI and the Justice Department.
He said the investigation is "being treated as a serious national security matter."
"There is evidence to indicate that we have seen destructive activity with malicious intent that was initiated by a sophisticated actor," Earnest said.
North Korea winning a cyber war?
He said the United States' response would need to be "proportional," and that national security officials considering how to respond are "also mindful of the fact that sophisticated actors when they carry out actions like this are oftentimes, not always, but often seeking to provoke a response from the United States."
A senior administration official said the White House did not pressure Sony to make the decision it announced Wednesday to pull the movie "The Interview" - which depicts the assassination of North Korean leader Kim Jong Un - from theaters.