Europe's threat to trigger a mechanism that could reimpose United Nations sanctions on Iran marks a significant breakdown in diplomacy to try to save the 2015 nuclear deal and could presage its death knell, diplomats say.
Britain, France and Germany have sought to salvage the pact, under which Iran undertook to curtail its uranium enrichment program in return for relief from sanctions crippling its economy, since the United States withdrew last year.
But the three European powers have failed to make good on the trade and investment dividends promised to Iran under the deal as they have been unable to shield Tehran from renewed U.S. sanctions that have strangled its vital oil trade.