What would it mean for Russia, if the United States really did launch “harder” sanctions “than we’ve ever seen before” against its economy?

That was the threat issued by Lt Gen Keith Kellogg, the US special envoy to Ukraine, in an interview with Fox News on Tuesday.

Lt Gen Kellogg said Vladimir Putin had been warned that drastic new US sanctions were ready to go, should he come to be seen as the main obstacle to peace.

European leaders would act in tandem with the president, he said, having had a “good phone call” on the subject last week.

It remains the overwhelming likelihood that, come the talks in Istanbul on Thursday, Putin fails to engage in anything but prevarication. He is not expected to attend in person.

Volodymyr Zelensky therefore has the chance to further convince Washington that Russia – not Ukraine – is to blame for the continuation of the war.