"It's unacceptable, they [Ukraine] need to tone it down and take a hard look and sign that deal," he tells Fox News. The deal he is referring to is a push by Donald Trump for access to rare minerals in Ukraine in return for aid, or even as compensation for the support the US has already provided.

As the Trump administration works toward a halt in the fighting, many experts fear that Ukraine will be forced to accept a ceasefire deal that will only give Russian forces a badly needed breather.