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 on Tehran.
After months of negotiations in Vienna, a revised deal was expected to be reached within days under which US sanctions would be lifted in return for Tehran returning to full compliance with the 2015 nuclear nonproliferation deal.
