Positive signals from Iran over nuclear deal put west in a tricky position

Revival of pact could mean lifting sanctions on a country that is viciously suppressing protests and arming Russia

Wary western powers face an unlikely potential dilemma after a sudden push by Tehran to suggest that progress is being made to remove the last outstanding obstacles to a revived agreement to oversee Iran's nuclear programme.

The unlikely prospect of Joe Biden reviving the dormant 2015 nuclear deal, potentially lifting sanctions and opening the way for Iran to make billions of dollars in oil exports, would be seen as a gross betrayal by supporters of three-month-long street protests, as well as a controversial signal to send to Ukraine about Washington's priorities.