Iran nuclear talks rocked by Russian demand for sanctions exemption

Russia seeks guarantees regarding trade with Iran that would undermine west's sanctions over Ukraine invasion

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 non-proliferation deal.