Muenster, Germany  - As European leaders close ranks to salvage the Iran nuclear deal, German Chancellor Angela Merkel called US President Donald Trump's move to exit the accord of "grave concern."

Merkel told an audience at a major Catholic religious gathering - the theme of which was peace - that Trump's decision to pull the US out of the Iran nuclear deal "damages trust in the international order."

EU leaders try to save the deal

While saying it was "far from perfect," she told the audience in the German city of Muenster that she believed "it is not right that a deal which was agreed, which was voted upon in the UN Security Council and unanimously approved, should be unilaterally terminated."

Trump pulled out of the 2015 agreement sealed by his predecessor, president Barack Obama - with the support of China, Russia, Germany, France and Britain - on Tuesday.

The deal lifted economic sanctions on Tehran in exchange for commitments to halt what Western powers feared was a nuclear weapons programme. N

With European businesses that have commercial ties to Iran now in the firing line of renewed US sanctions, European leaders are scrambling to save the deal.

The foreign ministers of Germany, France and Britain are due to meet their Iranian counterpart Mohammad Javad Zarif in Brussels on Tuesday, together with EU foreign policy chief Federica Mogherini, her office announced.

But such efforts have been undermined by escalating military conflict between Iran and Israel in recent days.

On Thursday, Israel accused Iran of firing a barrage of rockets on Israeli military positions across a ceasefire line in southern Syria.

Israel hit back with dozens of airstrikes that it said hit "almost all" Iranian military infrastructure in Syria.

Despite raised eyebrows over Iranian behaviour, France said it remains undeterred in their attempt to save the deal.

"We condemn any attempt to harm Israel's security," French Foreign Minister Jean-Yves Le Drian said in an interview in Friday's edition of newspaper Le Parisien.

Deal important to security and stability

Nevertheless, Le Drian said that the agreement on Iran's nuclear activities remained in force, though he added that France wants to complement it with new measures on issues such as Iran's ballistic missiles.

Asked how he could reassure Iranian citizens, he said: "We are faithful to our commitments. We have expectations, but we're here."

Another one of the deal's signatories, Russia, also reasserted their commitment to the deal during a phone call between Merkel and Russian President Vladimir Putin.

The deal between Iran and the international community is of "fundamental importance" to security and stability in the region, the two leaders agreed in the conversation, according to a Kremlin statement.

Though leaders are presenting a united front on the world stage, some face domestic dissent from sceptics who believe the deal can't be saved, and that European businesses that have invested in Iran could be hurt by renewed US sanctions.

In Germany, Norbert Roettgen, the conservative chairman of the parliamentary committee for foreign affairs, told magazine Focus that "It (the deal) won't work without the Americans."

If Iran stays in the deal, Roettgen said, it will expect European companies to make up for the shortfall caused by US companies pulling out.

"At the end of the day it's a business decision. If European companies have to choose between the Iranian and American market, most will find the US market to be more important,"