Iran’s clerical rulers are facing one of their gravest crises since the 1979 Islamic Revolution, caught between growing discontent at home and a stalled nuclear deal that together have left the country more isolated and divided.

The United Nations reimposed sanctions on Iran on Saturday after last-ditch talks between Tehran and European powers Britain, France and Germany failed to resolve the latest of decades of standoffs over Iran's nuclear program.

Without a breakthrough in talks with the West, four Iranian officials and two insiders predicted Iran's economic isolation would further intensify, stoking public fury.