The United States was not responsible for network outages in North Korea that crippled the country's Internet infrastructure in December, The Associated Press (AP) reported, citing two senior U.S. officials. The U.S. government had not openly denied if it was involved in the failure of North Korea's internet network. 

The comments of the officials, who spoke on condition of anonymity, come soon after President Barack Obama said his administration will respond to the massive computer hack of Sony Pictures Entertainment Inc.

North Korea's Internet services, which rely mainly on China United Network Communications Group Co. Ltd., had completely collapsed for nearly 10 hours, two days after they were faced intermittent outages since Dec. 20.

Sony’s CEO Michael Lynton also reportedly denied having knowledge about whether the U.S. attacked the North Korean networks as retaliation for the attack on his company. Hackers had earlier threatened to disclose Sony's confidential documents if it released the film, "The Interview," based on a fictional plot to assassinate North Korean leader Kim Jong Un. Sony had earlier canceled the movie's Dec. 25 release due to the hack. But, it reversed course and released it in 350 small theaters and through online distribution channels after public pressure and criticism from Obama.

"It looks more like the result of an infrastructure attack than an infrastructure failure," James Cowie, chief scientist at Dynamic Network Services Inc. of Manchester, New Hampshire, who studied the outages, said, according to AP, adding: "There's nothing you can point to that says it has all the hallmarks of an attack by a nation state. It could have been anybody."

The U.S. government had so far only hinted that it was not involved in the network outages. Lisa Monaco, Obama's homeland security adviser, reportedly refused to comment on the matter. "I'm not going to comment, and I never would, on operational capabilities," Monaco said, according to AP, adding: "But you want to be able to have a number of tools in our toolbox and reserve them for use."

North Korea had accused the U.S. of being behind the Internet disruptions, but Washington did not deny or accept the allegations then.

"The United States, with its large physical size and oblivious to the shame of playing hide and seek as children with runny noses would, has begun disrupting the Internet operations of the main media outlets of our republic," North Korea’s National Defense Commission had reportedly said at the time.