While the president is required to certify the deal every 90 days, that certification is not part of the deal.
Meeting with officials from the Trump and Obama administrations, European diplomats and among themselves, they have been preparing strategies to save it, including pushing for tougher inspections, changing the law requiring Trump to certify Tehran's compliance and setting new sanctions over Iran's non-nuclear activities.
President Trump's upcoming decision on how he will deal with the risky and flawed nuclear agreement is a moment for moral clarity and may be a defining moment of his presidency. Under a new version being negotiated with Congress, he would have to endorse the deal less frequency but the U.S. intelligence community would have to assess whether Iran is carrying out covert activity in facilities not visited by the IAEA.
"As flawed as the deal is, I believe we must now enforce the hell out of it", said the California lawmaker.
Trump's administration, which took over a year after the nuclear agreement had come into force, has repeatedly attacked the agreement and desperately sought a pretext to scrap or weaken the deal.
Daniel Kurtzer, a former USA ambassador to Israel who is now a professor at Princeton University, said the political pressure could be intense.
It also would indicate that the United States would be willing to renegotiate agreements with every new administration, giving other countries reason to hesitate on negotiations if they felt future leadership would give them a better deal, Mogherini added.
Trump allies who oppose the deal have watched the president closely to see if he might buckle under pressure.
In anticipation of Trump's announcement this week, advocacy groups are beginning to mobilize in support of the agreement, and in opposition to Trump's reckless moves to undermine and dismantle it. The agreement has been beneficial for Iran's economy, opening it to foreign markets and the global financial system, said Ahmad Khalid Majidyar, who previously taught Middle East issues to USA and North Atlantic Treaty Organisation military leaders at the Naval Postgraduate School's Leader Development and Education for Sustained Peace program. "Once it was entered into, once it was implemented, we want to see it enforced".
The certification would also demand that the intelligence community produce judgments on a wide range of Iranian behaviour that is not covered by the nuclear deal, including ballistic missile testing and development, support for Lebanon's Hezbollah movement and Syrian President Bashar Assad and threats to Israel and the Mideast more broadly, according to the drafts. He would not say whether he would be open to other changes, stressing new conditions might violate the deal.
What happens if Trump decertifies the deal?
But France, the United Kingdom, Germany, and the European Union - who negotiated the deal along with the U.S., China, Russia, and Iran - have all said the deal is working well and urged the U.S.to stay in it.
First, Congress could vote to snap sanctions back into place, or Trump could refuse to sign the next round of waivers for sanctions.
Officials familiar with the internal deliberations as well as informed sources outside the administration say they do not believe Trump will call for Congress to reinstate the sanctions. Those provisions relate to enriching uranium to levels near those needed to produce the fuel for a nuclear weapon, as well as other activities that limit Iran's atomic capabilities at various sites.
Trump threatened during the presidential campaign to tear the pact up if he was elected.