FRANCE, Germany and Britain have agreed to restore tough United Nations sanctions on Iran by the end of August if there has been no concrete progress on a nuclear deal, two European diplomats said on Tuesday.

The three countries’ ambassadors to the UN met on Tuesday at Germany’s UN mission to discuss a possible Iranian deal and reimposing the sanctions.

The matter also came up in a phone call on Monday between United States Secretary of State Marco Rubio and the foreign ministers of the three countries, according to two US officials.

The State Department said after the call that the four had spoken about “ensuring Iran does not develop or obtain a nuclear weapon.”

The officials and diplomats spoke on condition of anonymity to discuss private conversations.

France, Germany and Britain are part of an agreement reached with Iran in 2015 to rein in its nuclear programme, from which President Donald Trump withdrew the US during his first term, insisting it wasn’t tough enough.

Under the accord that lifted economic penalties on Iran in exchange for restrictions and monitoring of its nuclear programme, a so-called “snapback” provision allows one of the Western parties to reimpose UN sanctions if Tehran does not comply with its requirements.

French Foreign Minister Jean-Noel Barrot said: “Without a verifiable commitment from Iran by the end of August at the latest, France, Germany and Britain will be justified in reapplying the UN sanctions [snapbacks] that were lifted 10 years ago.”

The diplomats did not provide details of the deal being sought. Iranian Foreign Minister Abbas Araghchi said in recent days that Tehran would accept a resumption of nuclear talks with the US if there were assurances of no more attacks, following Israeli and US strikes on its nuclear facilities.

Iran’s UN mission had no comment Tuesday on the threat of renewed sanctions if there is no deal.