The United States and Australia will announce cooperation on cyber warfare as the close allies mark 60 years of a defence treaty by tackling 21st-century threats.

US and Australian foreign and defence ministers will add the issue to their joint security treaty during talks Thursday in San Francisco, where the nations first signed the agreement in 1951, US Defence Secretary Leon Panetta said yesterday.

Pentagon officials said it was the first time cyber warfare had been formally addressed in any bilateral US defence treaty, although the NATO alliance has focused on cyber threats.

"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 aboard his plane before arriving in San Francisco.

The Pentagon chief also suggested America and its allies would have to look at offencive operations in the digital arena, a subject US officials have been reluctant to speak about in detail.

"We are 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," he said.

"The best way to accomplish that is not only on our own but working with our partners," he added.

Panetta said the talks with Australian officials would also look at bolstering cooperation on space and missile defence projects.

Australian Defence Minister Stephen Smith, in a statement ahead of the talks, called cybersecurity "the key emerging transnational threat of the 21st century" and said it would be a major feature of the annual talks.

Cyber warfare marks the latest update for the evolving alliance, which was initially focused largely on Australia's security but has become increasingly global. Australia notably stations some 1,500 personnel in Afghanistan.