The United States is seriously concerned about cyber-attacks and is prepared to use force against those it considers acts of war, Defense Secretary Robert Gates said at a security meeting in Asia on Saturday.

He also assured Asian allies that the United States would protect sea lanes and maintain a robust military presence in the region despite a severe budget crunch and the protracted wars in Iraq and Afghanistan.

We take the cyber threat very seriously and we see it from a variety of sources, not just one or another country, Gates said at the annual Shangri-La Dialogue, an apparent reference to reports that several of the attacks may have originated in China.

What would constitute an act of war by cyber that would require some kind of response, either in kind or kinetically? he said.

We could avoid some serious international tensions in the future if we could establish some rules of the road as early as possible to let people know what kinds of acts are acceptable, what kinds of acts are not and what kinds of acts may in fact be acts of war.

Earlier this week, Google said it had disrupted a campaign aimed at stealing passwords of hundreds of Google email account holders, including senior U.S. government officials, Chinese activists and journalists.

It was the latest in a series of cyber attacks that have also targeted defense contractor Lockheed Martin and Sony Corp. Google said the latest breach appeared to originate in China but neither the company nor the U.S. government has said the Chinese government was responsible.

But the U.S. State Department has asked Beijing to investigate.

British Defense Secretary Liam Fox said cyber attacks were now regular and in large numbers. It's....the war of the invisible enemy, he said, adding that it had become a matter of urgency and was firmly on top of the security agenda.

CHINA TIES

Gates said it was difficult to identify where the perpetrators of such attacks were based and added that military ties with China were improving.

But he also said the U.S. was preparing weapons systems and capabilities that would allow U.S. forces to deploy, move and strike over great distances in defense of our allies and vital interests. Although he gave few other details, the plans could worry China, U.S. officials privately said.

Asked whether China wouldn't see the remarks as a concern, a senior U.S. defense official said it was an example of the need for greater military transparency between the two sides.

Without transparency, we obviously have to do certain things and make certain preparations because it's not quite clear what everybody's intentions are, the official said. So the more ... clear it is about what China's military investment is aimed at, the more clear it us for us what's going on in the region and what intentions are.

Gates said the United States was committed to its Asian allies although a decade of combat in Iraq and Afghanistan had strained U.S. ground forces and exhausted public patience, while the recession had left Washington with huge budget deficits and looking to cut military spending.

Irrespective of the tough times the U.S. faces today, or the tough budget choices we confront in the coming years, ... America's interests as a Pacific nation -- as a country that conducts much of its trade in the region -- will endure, he said.

The United States and Asia will only become more inextricably linked over the course of this century. These realities ... argue strongly for sustaining our commitments to allies while maintaining a robust military engagement and deterrent posture across the Pacific Rim, he said.

(Additional reporting by Kevin Lim and Sanjeev Miglani; Editing by Jonathan Thatcher)

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