The United States has sought help from China, Japan, South Korea and Russia in combating cyber attacks such as the one Washington on Friday accused North Korea of carrying out against Sony Pictures, U.S. officials said.
The outreach, which included meetings among U.S. and Chinese officials in both nations' capitals, is a tacit acknowledgement that if anyone has influence over Pyongyang it is China, given its long border, historical ties and quiet trade with the North.
U.S. officials and outside analysts said Washington has little choice but to try to enlist China's help because of its economic ties to the North, which is largely isolated from the United States.
"The sanctions on North Korea are very different from the ones on Iran and Russia because the North Korean economy is so isolated and so dependent on China and on illegal arms sales," said a U.S. official who spoke on condition of anonymity.
U.S. President Barack Obama on Friday said he would respond "proportionally" to the attack on the Sony Corp studio, which brought down the firm's computer network and led it to cancel the Christmas day release of "The Interview," a movie which culminates in a scene depicting the assassination of North Korean leader Kim Jong Un.
He declined to say how he might retaliate but said it would be "in a place and time and manner that we choose."
James Lewis, a cyber security expert at the Center for Strategic and International Studies think tank, said all the countries were interested in collaborating on the issue.
"None of them want an armed conflict and none of them want North Korea to collapse. They are all worried that this could somehow lead to a war and none of them want that," Lewis said, adding that North Korea enjoys "a strange kind of immunity."
Earlier, a U.S. official who spoke on condition that he not be named said that there might be a Chinese link in the attack either through North Korea's collaboration with Chinese actors or by its using Chinese servers to mask the origin of the hack.
In public, U.S. officials stressed that they had no evidence of the Chinese government's involvement in the hack and Obama said the United States had "no indication that North Korea acted in conjunction with another country."
A spokesman for the Chinese embassy said Beijing, which has clashed with repeatedly with Washington over cyber spying, believed in cooperation on cyber security.
"Chinese laws prohibit cyber crimes of all forms and Chinese government has done whatever it can to combat such activities. Any individual is not allowed to commit cyber illegalities in any part of China," he said.
One analyst suggested the mere mention of a possible Chinese link, albeit by an anonymous U.S. official, may be Washington's way of nudging Beijing to do more to rein in the North.
"It is a very deliberate signal both to hint at the extent of U.S. evidence about this hack as well as to put China on notice of the U.S. desire to see China cooperating," said Frank Jannuzi, president of the Maureen and Mike Mansfield Foundation, which seeks to promote understanding of U.S.-Asia relations.
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