The US has warned Russia of “catastrophic consequences” if it uses nuclear weapons in its war against Ukraine. The statement comes after Russian President Vladimir Putin insisted he’d use “all the means at our disposal to protect Russia and our people”, adding this is “not a bluff”. The threat of escalation feels more acute after Moscow reported four self-styled referendums held in Russian-held regions of Ukraine showed near universal public support for joining Russia. So, if Ukraine continues to try to wrest back full control of the regions, is it possible the Kremlin could respond with the use of small ‘tactical’ nuclear weapons? Ritula Shah is joined by a panel of expert guests. Producers: Paul Schuster and Ellen Otzen.