Days after US President Donald J. Trump announced that he would buck international protocol and unilaterally pull the United States out of a landmark deal that helped curb Iran’s nuclear weapons programme, the European Union has been forced to ponder how it will respond to a threat issued by Trump’s White House on May 13 that Washington would impose stiff economic sanctions on European companies that continue to do business with Tehran.

Iranian Foreign Minister Mohammad Javad Zarif is heading to Brussels to meet with the EU’s foreign policy chief, Federica Mogherini, after previous stops in Beijing and Moscow to discuss the current situation following Trump’s announcement. EU members France, the UK, and Germany are signatories to the agreement along with Russia and China – who, aside from Berlin, are also permanent members of the UN Security Council with the United States.

Mogherini will host a consultation of German, French, and British foreign ministers on May 15 to discuss the future of the Iran accord and the US’ latest threat. Britain, France, Germany, Russia, and China had tried to convince Trump to keep the US in the deal, saying it was the best way to prevent Iran from developing nuclear weapons.

Trump, however, refused to heed the warnings of his counterparts around the world and ignored the advice of his own defence secretary, retired Marine general Jim Mattis, as well as his allies in NATO and the US’ intelligence community – both of whom Trump has publicly insulted and clashed with on numerous occasions since he came into office in January 2017.

In statements prior to his decision to withdraw from the agreement and to re-impose crippling economic sanctions on Iran, Trump said he had no intention of changing course on a campaign promise that he made nearly two years ago when he pledged to reverse his predecessor Barack Obama‘s landmark accord with Tehran.

Trump’s newly-named National Security Adviser John Bolton said that it is “possible” that the US would sanction European companies that maintain business dealings with Iran, a statement that received a lukewarm reaction from Secretary of State Mike Pompeo, who said he remained hopeful that Washington and its allies European could strike a new deal with the Iranian government.

Bolton, one of the key architects of the George W. Bush administration’s decision to invade Iraq in 2003, despite lacking evidence that Iraq’s Saddam Hussein had a programme to develop weapons of mass destruction, stuck to his famously more hawkish tone with comments that hinted that trump’s White House would consider any European company that continues to honour legally binding business contracts with Iran as hostile acts.

UK Prime Minister Theresa May has reportedly told Iran’s moderate President Hassan Rouhani that Britain and its European partners remain committed to ensuring that the nuclear deal with Iran remains in place and that Tehran must continue to meet its obligations under the pact, a pledge that both Rouhani and Foreign Minister Zarif said Iran plans to keep.

Germany, the UK, and France have significant trade links with Iran and remain committed to the nuclear agreement. German Chancellor Angela Merkel said the remaining participants in the deal need to discuss with Tehran ways to save the agreement that may have to include sanctions-blocking measures that France’s Finance Minister Bruno Le Maire said would be discussed with the European Commission.