The massive hacking of Sony Pictures Entertainment and a threat against movie theaters showing the studio's film "The Interview" may backfire for North Korea, even though Pyongyang has denied involvement in the incidents.

The Associated Press reports policymakers in Washington are calling for even tougher sanctions against the isolationist regime and for the country to once again be added to the U.S. list of state sponsors of terrorism.

California Rep. Ed Royce, the Republican chairman of the House Foreign Affairs Committee, said he believed North Korea was involved in the Sony attack and wants to cut the country's access to hard currency by denying it access to U.S. financial system banks in other countries that hold North Korean funds.

"This is not a just a corporate security issue,'' Royce said. ''It is an act of aggression against the United States by a foreign government."

Evans Revere, a former State Department official and specialist on Korea, said putting Pyongyang back on the list of terror states would be "warranted."

Currently, the United States only designates Cuba, Iran, Sudan and Syria in that fashion. As a concession during nuclear negotiations, the Bush administration took North Korea off the list in 2008.

The hacker group claiming responsibility for the threats made against "The Interview" -- a film that portrays North Korean dictator Kim Jong Un in a negative light -- had warned moviegoers of Sept. 11-style terrorist attacks.

The White House, which had long been mum on the rumors of North Korean involvement, on Friday publicly implicated Pyongyang and provided "the most detailed accounting to date of a hugely expensive break-in that could lead to a U.S. response," The Associated Press noted.

The FBI said in a statement it now has sufficient evidence that Kim's regime was behind the breach, which led to the publication of tens of thousands of leaked emails and distribution of unreleased Sony movies.

"North Korea's actions were intended to inflict significant harm on a U.S. business and suppress the right of American citizens to express themselves," the FBI said. "Such acts of intimidation fall outside the bounds of acceptable state behavior."