Having spent months lobbying US President Donald Trump unsuccessfully over the Iran nuclear deal, European countries are now scrambling behind the scenes to save an agreement negotiated through painstaking diplomacy.
Trump is set to announce his position on the 2015 accord as early as Thursday having spent the past two years disparaging a key foreign policy breakthrough of his predecessor, Barack Obama, as "the worst deal ever."
Most analysts expect him to declare that Tehran is failing to live up to its commitments -- a view not shared by the other five world powers involved in the talks.
A decision by Trump to "decertify" the deal would leave it at grave risk with the US Congress having 60 days to decide whether to re-impose specific sanctions on Tehran that were lifted because of the diplomatic pact.
"At a legal level the deal would not -- yet -- be dead, but politically the signal is very strong," said one European diplomat speaking about Trump's expected decision to de-certify.
"This agreement is also a deal that depends on confidence," the diplomat said, asking not to be named because he was not authorised to speak publicly.
The deal, which formally took force in January 2016, was designed to stop Iran gaining atomic weapons -- an objective Tehran has always denied pursuing.
Under the deal, Tehran agreed to mothball large parts of its nuclear programme.
- Unwilling to listen? -
Trump's comments on the Iran deal have reinforced perceptions of his administration as unpredictable and deaf to the views of Europe's main powers, which have historically been America's closest allies.
Both British Prime Minister Theresa May and French President Emmanuel Macron used the United Nations General Assembly in September to try and change the 71-year-old US leader's mind on Iran -- to little effect.
"Frankly, that deal is an embarrassment to the United States," Trump told the General Assembly.
Europe's efforts recall the fruitless campaign to persuade Trump to respect the 2015 Paris agreement on climate change, which also saw concerted efforts in private and public from France, Britain and Germany.
Finding the White House impervious to their reasoning, European diplomats are now focusing their attention on members of the Republican-dominated US Congress.
"Our embassy is working with the legislature," German foreign ministry spokesman Rainer Breul said earlier this week. "We are looking for dialogue, to explain our arguments and why in our opinion the Iranian deal is a success."
- Blow to trade -
European companies have moved into Iran over the last year, keen to tap a growing and potentially lucrative market but still wary about some US financial sanctions which remain in place.
French firms have been at the forefront, with oil group Total and carmakers Renault and Peugeot announcing investments of several billion euros.