Iran's clerical rulers face one of their gravest crises since the 1979 Islamic Revolution, caught between growing discontent at home and a stalled nuclear deal that 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.

Yet accepting the West's demands risks fracturing the ruling elite and sidelining the Islamic Republic's revolutionary beliefs in "not succumbing to Western pressure" that define Tehran's

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