The official warns that from Putin's vantage point, though, deep dissatisfaction with the situation in Ukraine and fear of the west turning the tide might actually provoke a nuclear display of some sort—one intended to shock the west and bring a halt to the war. The supply of western arms is also now a serious game changer, resupplying Ukraine while Russia is increasingly constrained. "Escalation is now a true danger," says the senior official.

Nina Khrushcheva said she fears Russian President Vladimir Putin will eventually deploy tactical nuclear weapons to claim victory in Ukraine.