A major international diplomatic effort is being mounted to try to save the Iran nuclear deal from collapse in the wake of Donald Trump’s withdrawal.

Federica Mogherini, the EU’s foreign policy head, said the bloc was determined to keep the 2015 agreement in place and she is due to lead talks between the foreign ministers of four countries in the pact next week.

Representatives from Iran, the UK, France and Germany are to meet in Brussels on Tuesday.

The summit will follow a string of phone calls between leaders in which they talked up efforts to preserve the deal.

Vladimir Putin and Angela Merkel spoke on Friday, a week before the German chancellor travels to Sochi, and agreed they would work to maintain the deal while seeking to avoid an escalation of regional tensions.

Emmanuel Macron is also due to visit Russia later this month. During a state visit in Washington, the French president had lobbied Mr Trump hard to stay in the Iran pact.

Mr Trump spoke to Theresa May on the phone on Friday, after which Downing Street said the prime minister “reiterated the government’s position on the Iran nuclear deal, noting that we and our European partners remain firmly committed to ensuring the deal is upheld as the best way of preventing Iran from developing a nuclear weapon”.

Meanwhile thousands of Iranians protested across the country on Friday against Mr Trump’s decision to remove the US from the nuclear agreement. France, Germany, Britain, Russia and China are the remaining signatories, alongside Iran.

Many Iranians angered by Mr Trump’s decision are now siding with hardliners who advocate suspicion of the West.

On Friday evening, the Iranian government warned it would take “whatever reciprocal measures it deems expedient” if it is not fully compensated for the US withdrawal from the nuclear agreement.

A lengthy statement called on the other countries – especially the three European powers – to safeguard the accord, implement their commitments, and “proceed from giving pledges to taking practical action without any preconditions”.

Israel attack Iran targets in Syria: overnight airstrike in pictures Show all 10 1 /10 Israel attack Iran targets in Syria: overnight airstrike in pictures Israel attack Iran targets in Syria: overnight airstrike in pictures Missiles rise into the sky as Israeli missiles hit air defense position and other military bases, in Damascus Syrian Central Military Media, via AP Israel attack Iran targets in Syria: overnight airstrike in pictures Missile fire is seen from Damascus Reuters Israel attack Iran targets in Syria: overnight airstrike in pictures An Israeli flag is seen placed on Mount Bental in the Israeli-annexed Golan Heights. Israel's army said today it had carried out widespread raids against Iranian targets in Syria overnight after rocket fire towards its forces it blamed on Iran, marking a sharp escalation between the two enemies. Israel carried out the raids after it said around 20 rockets, either Fajr or Grad type, were fired from Syria at its forces in the occupied Golan Heights at around midnight. AFP/Getty Israel attack Iran targets in Syria: overnight airstrike in pictures The Israeli military on Thursday said it attacked "dozens" of Iranian targets in neighboring Syria in response to an Iranian rocket barrage on Israeli positions in the Golan Heights AP Israel attack Iran targets in Syria: overnight airstrike in pictures Israeli artillery deployed missiles toward Syrian military targets, on the Golan Heights EPA Israel attack Iran targets in Syria: overnight airstrike in pictures Missile fire is seen over Daraa Reuters Israel attack Iran targets in Syria: overnight airstrike in pictures Air defence systems intercepting Israeli missiles over Syrian airspace AFP/SANA Israel attack Iran targets in Syria: overnight airstrike in pictures Israeli soldiers walk among armored vehicles in the Israeli-occupied Golan Heights Reuters Israel attack Iran targets in Syria: overnight airstrike in pictures Syrian air defense missiles are seen in the sky over the capital Damascus EPA Israel attack Iran targets in Syria: overnight airstrike in pictures Air defence systems intercepting Israeli missiles over Syrian airspace. Israeli missile strikes fired at Syria hit military bases, as well as an arms depot and military radar. AFP/SANA

Iran reiterated that no provisions or time frames set out by the 2015 agreement “are negotiable in any manner”. It also reiterated its foreign minister was seeking “required guarantees” from the five other parties to the agreement as well as Iran’s other economic partners.

At the same time, the government said it had tasked the president of the Atomic Energy Organisation of Iran with “taking all necessary steps in preparation for Iran to pursue industrial-scale enrichment without any restrictions”.

The statement was sharply critical of Mr Trump, calling his administration “extremist” and the US withdrawal from the accord “unlawful”. It said the decision had damaged Washington’s credibility on the world stage and the credibility of other accords it has signed, and put “the present system of international law in serious danger”.