US President Donald Trump has announced the withdrawal of the United States from the Iran nuclear deal.
Speaking at a press conference at the White House, he also announced the re-establishment of US sanctions against Iran.
The Joint Comprehensive Plan of Action was signed by Iran and six world powers in 2015 after lengthy negotiations.
It eased economic sanctions on Iran in exchange for Tehran limiting its nuclear programme.
Mr Trump has repeatedly threatened to withdraw from the deal, unless France, Germany and Britain, which also signed the agreement, fix what he has called its flaws.
A senior US official said the European allies had moved significantly in Mr Trump's direction on what he sees as the defects - the failure to address Iran's ballistic missile programme, the terms under which international inspectors visit suspected Iranian sites, and "sunset" clauses under which some terms expire.
However the official did not know if the Europeans had done enough to convince Mr Trump to remain in the deal.
"The big question in my mind is does he think the Europeans have moved far enough so that we can all be unified and announce a deal? That's one option," said the official.
"Or (does he conclude) the Europeans have not moved far enough and we say they have got to move more?"
European diplomats said privately they expected Mr Trump to effectively withdraw from the agreement.
"It's pretty obvious to me that unless something changes in the next few days, I believe the president will not waive the sanctions," one European diplomat said, adding he saw only a "very small" chance that Mr Trump would stay in the deal.
European leaders have warned that Mr Trump's withdrawal would strike a blow to the alliance between western Europe and the United States, and undo years of negotiations that they say were successful in halting Iran's nuclear ambitions.
Iran has ruled out renegotiating the accord and threatened to retaliate, although it has not said exactly how, if the US pulls out.
Mr Trump gave no indication of which way he was leaning yesterday, saying only in a Twitter post that he would announce his decision at 2pm (7pm Irish time).
Under the deal, the US committed to easing a series of US sanctions on Iran and it has done so under a string of "waivers" that effectively suspend them.
Under US law, Mr Trump has until Saturday to decide whether to reintroduce US sanctions related to Iran's central bank and Iranian oil exports.
The re-imposition of sanctions would dissuade foreign companies from doing business with Iran because they could be subject to US penalties.
Bringing back US sanctions could also trigger a backlash by Iran, which could resume its nuclear arms programme or punish US allies in Syria, Iraq, Yemen and Lebanon, diplomats said.
Yesterday, Iranian President Hassan Rouhani suggested Iran could remain in the accord even if the US dropped out but that Iran would fiercely resist US pressure to limit its influence in the Middle East.
Mr Rouhani said Iran had been preparing for every possible scenario, including a deal without the US, which would still include the other signatories that remain committed to it, or no deal at all.
"We are prepared for all scenarios and no change will occur in our lives next week," Mr Rouhani said in a speech broadcast live on state TV.
Britain, France and Germany remain committed to the accord and, in an effort to address US complaints, want to open talks on Iran's ballistic missile programme, its nuclear activities beyond 2025 - when pivotal provisions of the deal expire – and its role in the wars in Syria and Yemen.
British Foreign Secretary Boris Johnson, in Washington this week, said the deal's weaknesses could be remedied.
"At this moment Britain is working alongside the Trump administration and our French and German allies to ensure that they are," he said.
Mr Johnson met US Secretary of State Mike Pompeo and Vice President Mike Pence yesterday.
What do we all think? Personally I may not be the biggest Iran fan but I think it's a bit of a fallacy to presume this marks a shift in 'dealing with terrorists' considering close US-Saudi relations.