European countries are trying to prevent the Iran nuclear deal from falling apart. They acknowledged the situation is serious but said there is a "small window" of time to save the historic agreement.

France, Germany and Britain have sought to defuse tensions in the Middle East, which culminated in a plan for the U.S. to conduct air strikes on Iran last month. But Trump called it off at the last minute.

On Monday, French President Emmanuel Macron said he would speak to Iranian President Hassan Rouhani along with Russian President Vladimir Putin and U.S. President Donald Trump this week. The move is a part of a French initiative to stem escalating tensions.

British Foreign Secretary Jeremy Hunt had phone conversations with his U.S. and Iranian counterparts over the weekend. He insists "the deal isn't dead yet," and there is still a "small window to keep the deal alive."

In the contest to be Britain's next leader, Hunt believes Washington and Tehran are not looking for a war with each other. His rival, lawmaker Boris Johnson, says he would not currently back Washington if it took military action against Iran.

Britain, France and Germany issued a joint statement on Sunday calling for dialogue to resolve the crisis. Current EU diplomatic chief Federica Mogherini said the steps taken by Iran so far include enriching uranium above the ceiling set by the deal. But she said this is still reversible.

However, none of this means defusing the crisis will be an easy task.

Paris said Monday that a Franco-Iranian researcher had been detained in Iran over spying allegations and local authorities are denying consular access and details of her condition. Macron said he has yet to receive any "valid clarification" from Tehran.

Earlier, on July 4, British Royal Marines seized an Iranian oil tanker, accusing the ship of carrying oil to Syria and violating EU sanctions. Iran denied the tanker was bound for Syria and has threatened to seize a British ship in retaliation. The tanker has not been released although both parties said they are not seeking to escalate an already fraught situation.