President Donald Trump's campaign to beef up the Iran nuclear deal is forcing diplomats to address thorny issues that negotiators tabled during years of diplomacy to prevent Iran from developing an atomic weapon.
Those issues are now being addressed in high-stakes talks between Europeans, who are intent on preserving the accord, and the Trump administration, which believes the agreement is fundamentally flawed. The parties face a deadline in May imposed by Trump.
Americans and Europeans always intended to revisit those issues at some point, sanctions experts say. But the hard line adopted by the president has forced the trans-Atlantic partners to revisit them sooner than many expected.
Now, Europeans and Americans are racing to resolve their differences. Earlier this year, Trump said he will refuse to waive sanctions against Iran in May if his administration cannot reach an agreement with Europe.
That would effectively kill the deal, removing limits on Iran's nuclear program. On the economic front, it would upend plans by European industrial and energy giants to restore business ties in Iran and disrupt energy supplies from the country, OPEC's third-biggest oil producer.
The 2015 deal lifted sanctions against Iran in exchange for Tehran accepting limits on its nuclear program and allowing the International Atomic Energy Agency to inspect its facilities.
However, it did not address Iran's ballistic missile tests or its role in Middle East conflicts. Negotiators also structured the deal so that limits on Iran's nuclear activities expire in 10 to 15 years.
"Most of the people that were involved in the negotiations at the time had reservations about the deal and how to handle the rest of the issues," said Richard Nephew, the lead sanctions expert for the U.S. negotiating team and now a senior research scholar at Columbia University's Center on Global Energy Policy.
The U.S. team and negotiators from Germany, France and the U.K. had resolved to address those issues once they secured an agreement to halt Iran's alleged nuclear weapons development, according to Nephew.
The Europeans are seeking assurances that Trump will not back out of any deal they hammer out with their American counterparts, The New York Times reported earlier this week.
The European Commission declined to comment, saying it does not discuss leaks.
Meanwhile, the State Department has instructed U.S. diplomats to convey that any agreement must address Iran's missile program, assure international inspectors have access to Iranian military sites and extend the date when key provisions of the deal expire, according to a memo obtained by the Times.
Nephew says both U.S. and European negotiators supported a longer deal and more intrusive inspections, but Iran refused during negotiations and had the backing of Russia and China.
He warns that engaging in brinkmanship now — before Iran has seen significant economic improvement — could spoil the chances of getting the deal that Americans and Europeans wanted in the first place.
"The point of those who argue against a reckless dash against the JCPOA now — including the UK and French — is not that they wouldn't support a stronger deal, but rather that what we have is pretty good and that getting anything in the future is contingent on faithful implementation now," he said, referring to the deal's official name, the Joint Comprehensive Plan of Action.
Others believe the United States has waited long enough.
"The U.S. strategy is that we will not wait eight years until key aspects of the deal are about to expire to reach agreement on stopping Iran's sunset-enabled patient pathways to nuclear weapons," said Mark Dubowitz, CEO of the Foundation for Defense of Democracies and a critic of the current agreement.
Dubowitz says the United States and Europe are most likely to find common ground over Iran's ballistic missile tests, international inspections and Tehran's role in regional hotspots such as Iraq, Syria, Yemen and Lebanon.
The most difficult discussions will center around so-called sunset clauses, analysts say. These spell out the expiration of provisions that limit Iran's access to nuclear material and advanced technology. They provide a sort of insurance policy that Iran will not be able to quickly ramp up its nuclear program.
"The sunset clauses will be the toughest issue to address but must be resolved by May 12 or the president will walk away from the nuclear deal," said Dubowitz, who has advised the administration on the Iran deal.
Cliff Kupchan, chairman of risk analysis firm the Eurasia Group, agrees that the sunset clauses are a top priority at the White House, but he is not convinced the United States and Europe will be able to reach an agreement on the issue.
"What the Trump administration cares about is the sunsets, the sunsets and the sunsets, in no particular order, and that's not where Europe is," he said.
"Europe is not going to give Trump all he wants in making restrictions permanent."