Russia has been accused of trying to take the Iran nuclear deal hostage as part of its wider battle with the west over Ukraine, after it threw a last-minute spanner into plans for an agreement to lift a swathe of US economic sanctions.

Kyiv Post: Alexander, I’m glad to see you in Kyiv. Is this your home town? Alexander Vindman: I apologize that I don’t speak Ukrainian. I rarely do, I only studied the language for eight months in the war college 12 years ago.