Previously, a nuclear response has not been on the table for responding to most non-nuclear threats against the US.
But the language in this particular draft of the review could potentially allow for a nuclear response to a cyberattack on US infrastructure, the official noted.
While cyberattacks on the US are downplayed in the report, the official said, the implication is that there could be a US nuclear response if there was a devastating cyberattack on US infrastructure such as power grids, although that specific scenario is not mentioned.
Current US policy requires a lawful order
by the President to use nuclear weapons.
A lawful order is generally understood by the US military to mean any counterattack would have to be proportional to the threat in terms of damage and casualties of that attack against the US.
The story was first reported by The New York Times
President Donald Trump and Defense Secretary James Mattis have not yet signed off on a final version of what will be the first comprehensive review of US nuclear forces in nearly eight years.
The review, which would allow Trump to put his mark on the nuclear inventory for decades to come, could lead to more than $1 trillion in spending over nearly 30 years, according to an October 2017 report
from the Congressional Budget Office.
There have been three such reviews since the end of the Cold War, the most recent in 2010 under President Barack Obama.
Several US Defense officials have told CNN that the final draft -- expected to be unveiled just after Trump's State of the Union address on January 30 -- will likely focus on deterrence and reflect the greater threat from North Korea, which has stepped up its testing of missiles and nuclear devices over the last year, as well as an increased focus by Russia on its nuclear inventory.
The review is looking at current needs and capabilities across the US nuclear enterprise, including nuclear laboratories, stockpiles and manufacturing facilities. It is also studying future needs for modernizing aging nuclear weapons, including missiles, submarines and bomber aircraft.
The Pentagon's position is that without increased spending the government will be unable to produce and maintain a stockpile for land, sea, and air-launched nuclear weapons. Operations, interim upgrades and full modernization could cost $1.2 trillion, according the Congressional Budget Office report. The report estimates the fiscal needs could include:
- $313 billion for a new Columbia-class ballistic missile submarine that can fire nuclear missiles from beneath the ocean's surface.
- $149 billion for a new silo-based intercontinental ballistic missile and upgraded launch facilities.
- $266 billion for the new B-21 stealth bomber aircraft.
- Additional funding for weapons laboratories and command-and-control facilities.
The review could also recommend efficiencies and changes aimed at saving money, officials said.
Defense officials have told CNN that Trump is not expected to call for increases or modernization of the nuclear arsenal that would take the US beyond current arms control agreements.
However, experts say things to watch for in the review include possible recommendations to deploy small nuclear bombs abroad closer to anticipated conflict, or to develop more lower-yield nuclear weapons.
Experts, however, have worried that these kinds of developments could make the decision by a US president to use nuclear weapons easier.