Putin nuclear threat may not be a bluff: Pentagon

US officials have been war-gaming possible responses to a Russian atomic escalation in the seven-month conflict in Ukraine.

US Defence Secretary Lloyd Austin says there are no checks on Vladimir Putin. Picture: AFP

Russian President Vladimir Putin may not be bluffing with his threats to use nuclear weapons in Ukraine, the US Defence Secretary has warned.

Lloyd Austin spoke after it emerged that US officials have been war-gaming possible responses to a Russian nuclear escalation in the seven-month conflict.

Mr Putin was accused last week of “nuclear sabre-rattling” after he threatened to use Russia’s nuclear arsenal to protect Ukrainian territory annexed after illegitimate referendums.

“There are no checks on Mr Putin,” Mr Austin told CNN. “He made the irresponsible decision to invade Ukraine – he could make another decision.”

The White House has been examining responses including cutting Russia off from the world economy. A military response has been looked at, according to The New York Times, but it would probably be a counterstrike by Ukrainian forces with conventional weapons provided by the West. Mr Putin would probably not use nuclear weapons immediately, according to US officials who spoke to the newspaper. Instead, they suggested, Russia may start a cybersabotage campaign across Europe, target senior officials in Ukraine or strike its infrastructure.

Mr Putin’s nuclear threat may be intended to scare the West into rethinking its backing of Ukraine, or to force Kyiv to negotiate from a weakened position.

A Ukrainian military source said they did not believe the West would retaliate with a nuclear weapon, but would concentrate on preventing a Russian strike. The next few weeks, as Ukraine tries to take back the annexed areas, will be particularly risky.

HR McMaster, who was national security adviser to Donald Trump, said Ukrainian battlefield successes meant the nuclear threat was the “only quiver (Putin) has left”.

“I think the message to (Putin) is, if you use a nuclear weapon it’s a suicide weapon,” he said. “We ought to take it seriously. We have to, but we ought to not allow this to cow us in terms of the support for the Ukrainians.”

The Times