Washington: The Obama administration has sought China's help in blocking North Korea's ability to launch cyberattacks, the first steps toward the "proportional response" US President Barack Obama promised that would make Pyongyang pay for the assault on Sony Pictures - and as part of a broader move against future hacking, according to senior administration officials.

"What we are looking for is a blocking action, something that would cripple their efforts to carry out attacks," one official said.

US President Barack Obama has turned to China for help over the Sony hacking affair. Credit:Bloomberg

So far the Chinese have not responded. Their cooperation would be critical, since virtually all of North Korea's telecommunications run through Chinese-operated networks. It is unclear that China would choose to help, given tensions over computer security between Washington and Beijing since the Justice Department in May indicted five hackers working for the Chinese military on charges of stealing sensitive information from US companies.

The secret approach to China comes as US officials, convening a half-dozen meetings in the White House Situation Room last week, including one of the top national security team on Thursday night, developed options to give to the president during his vacation in Hawaii.