Russia is likely dialling up the threat of a nuclear attack in Ukraine. Russian commanders sans Vladimir Putn discussed using nuclear weapons in Ukraine last month.

The report adds that the commanders are also discussing the timing of using nuclear weapons for war.

Russia is yet to respond to the claims but the Kremlin spokesperson has repeatedly accused the West of deliberately pumping up the topic.

The White House said it had grown "increasingly concerned" about the potential use of nuclear weapons over the last few months.

But it stressed the US saw no sign of Russia preparing for such use. That chimes with earlier Western intelligence assessments that Moscow has not been moving its nuclear weapons.