On the eve of a deadline for the U.S. president to decide whether to reimpose oil sanctions lifted under the deal, the foreign ministers of the three European powers and EU foreign policy chief Federica Mogherini made their plea after their meeting in Brussels.
"The accord is essential and there is no alternative," France's Foreign Minister Jean-Yves Le Drian told reporters. "We do not hide the other points of disagreement (with Iran) that exist."
Tehran has always denied seeking nuclear arms.
British Foreign Secretary Boris Johnson, in a statement released before the start of the meeting in Brussels, called the nuclear deal a crucial agreement that makes the world safer.
Trumps October decision not to certify Irans compliance with the nuclear deal has put Washington at odds with all other signatories of the accord - Britain, France, Germany, Russia, China and the European Union.
European allies have warned of a split with the United States over the nuclear agreement and say if Washington reimposes sanctions on Iran, the pact could fall apart.
Trump must decide by mid-January whether to continue waiving U.S. sanctions on Irans oil exports under the terms of the pact. The U.S. State Department said on Tuesday the Trump administration was expected to decide on Friday.
The decision comes as Irans government deals with protests over economic hardships and corruption that are linked to frustration among younger Iranians who hoped to see more benefits from the lifting of sanctions
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