Iran ’s clerical rulers are facing one of their most serious challenges since the 1979 Islamic Revolution, with mounting domestic unrest and a stalled nuclear deal deepening the country’s isolation and divisions.

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 programme.

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 Tehr

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