The United States and Australia will take the rare step on Thursday of declaring the cyber realm as part of a mutual defense treaty, meaning that a cyber attack on one could lead to a response by both nations.

Defense and diplomatic chiefs from the United States and Australia are meeting in San Francisco some 60 years after the birth of the ANZUS military alliance, which commits Australia and the United States to support each other if one is attacked.

New Zealand has been an inactive partner of the alliance since 1985.

We will be releasing a joint statement saying that the ANZUS treaty applies to cyber space, a senior U.S. defense official said.

The treaty itself states that an armed attack in the Pacific on any of the countries would require each nation to act to meet the common danger, although there is no automatic trigger for a response.

It appeared to be the first explicit application of the cyber realm to a mutual defense treaty outside of NATO.

U.S. Defense Secretary Leon Panetta said applying the cyber realm to the treaty underscored the way the U.S. views the cyber threat.

I think it's in large measure a recognition of what I've been saying time and time again, which is that cyber is the battlefield of the future, Panetta said on Wednesday, speaking to reporters on his flight to San Francisco.

We're all going to have to work very hard not only to defend against cyber attacks but to be aggressive with regards to cyber attacks as well.

And the best way to accomplish that is not only on our own but by working with our partners.

The step is consistent with the Obama administration's cyber strategy released earlier this year, which acknowledged that certain cyber attacks could compel actions under the commitments of existing military treaties.

The U.S. military also has warned that a cyber attack could result in a real-world military response, presumably if it were devastating enough. So far, known cyber attacks on sensitive U.S. networks have focused on data theft.

The Pentagon disclosed in July that a foreign intelligence service stole 24,000 files from a U.S. defense contractor earlier this year.

Beyond the cyber announcement, Panetta and his Australian counterpart are expected to discuss expanding military cooperation, as part of a U.S. effort to enhance its posture in Asia.

Possibilities included increasing U.S. access to Australian training exercises and test ranges, potential pre-positioning of U.S. equipment in Australia, greater use by the United States of Australian facilities and ports, and options for joint military activities in the region.

We are looking to enhance our presence in Asia, not decrease it. And Australia would be part of that, the defense official said.

Still, the official doubted any big announcements on increased security cooperation would be made in San Francisco but acknowledged there could be clarity by the end of the year.

U.S. President Barack Obama will make his first visit to Australia since taking office -- after scrapping a visit twice last year because of domestic concerns -- from November 16-17.

(Reporting by Phil Stewart; Editing by Bill Trott)

Australia Barack obama Cybercrime Security