Redwood city, California: The United States defence secretary Ash Carter is due to unveil an updated cyber strategy on Thursday that will stress the military's ability to retaliate with cyber weapons, a capability he hopes will help deter attacks.

The strategy presents a potentially far more muscular role for the US military's cyber warriors than the Pentagon was willing to acknowledge in its last strategy rollout in 2011 and singles out threats from Russia, China, Iran and North Korea.

‘The United States must be able to declare or display effective response capabilities to deter an adversary from initiating an attack,’ according to a copy of the document, obtained by Reuters ahead of its release.

The Defense Department, it said, must develop ‘viable cyber options’ as part of the full range of tools available to the United States during heightened tensions or outright hostilities.

It should be able to use cyber tools to disrupt an enemy's command of networks, military-related critical infrastructure and weapons capabilities.

The full-throated acknowledgement of such possibilities in the unclassified document is a major shift from 2011 and reflects the US hope that it will help dissuade potential enemies.

Officials note that other tools to respond include publicly identifying nations responsible and imposing sanctions.

Carter, speaking to reporters flying with him to California, where he is due to meet Silicon Valley executives and speak at Stanford University, said the primary focus of the cyber strategy was defense.

But he acknowledged that the new strategy was ‘more clear and more specific about everything, including offense’.

‘It will be useful to us for the world to know that, first of all, we're going to protect ourselves,’ Carter said, noting that deterrence included ‘a threat to retaliate against those who do us harm’.

‘We obviously have a capability to do that, not just in cyber but in other ways’.

Carter's visit comes two months after President Barack Obama visited Silicon Valley, asking US executives for closer cooperation in defending against hackers after high-profile attacks on companies like Sony Pictures Entertainment.

‘The North Korean attack on Sony was one of the most destructive cyber attacks on a US entity to date’, the document said.

The document said Russia's cyber actors were stealthy but had unclear intentions and lambasted China's theft of intellectual property. Iran and North Korea had ‘less developed cyber capabilities’ but overt hostile intent toward US interests.