If Trump announces the decertification of the Iran nuclear deal, Congress will reportedly have 60 days to re-impose economic sanctions against Iran that were withdrawn following the 2015 agreement.
On Wednesday, head of the Atomic Energy Organization of Iran (AEOI) Ali Akbar Salehi said that Iran is considering "various scenarios" in response to Trump's "probable withdrawal" from the global nuclear deal. Trump is expected to declare that the deal is not in America's national interest.
While the Trump administration has twice certified Iranian compliance with the deal in notifications to the US Congress under an American law, the White House has indicated that a third verification - due later this week - would not be offered.
European officials have categorically ruled out renegotiating the deal, but have said they share Trump's concerns over Iran's destabilizing influence in the Middle East.
European allies have complained that the White House has not presented a plan on how to push back Iranian influence, particularly in Syria, where the Trump administration has insisted it did not want to get involved in the civil war, preferring to focus exclusively on fighting the Islamic State.
Mr. Trump's advisers also refused to present him with a thoughtful Iran deal exit strategy drafted by Ambassador John Bolton or to let Bolton meet with the president to brief this option.
"If the feeling is that the United States no longer supports the agreement, then the political reality is that the agreement will be in serious jeopardy and its implementation will be very hard", a senior French diplomat said. In exchange, the U.S., China France, the United Kingdom and Germany would relax economic sanctions each country imposed on Iran.
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. However, some members of Congress have expressed a willingness to hold off on sanctions to give Trump time to negotiate a strategy with the Europeans to alter the deal. "Once it was entered into, once it was implemented, we want to see it enforced". Tom Cotton, R-Ark., would demand that the intelligence community produce judgments on a wide range of Iranian behavior that is not covered by the nuclear deal, including ballistic missile testing and development and threats to Israel and the Mideast more broadly.
Iran has said it is open in principle to further discussions, particularly with Europe, but has said its missile programme is non-negotiable.
What happens if Trump decertifies the deal?
The Foreign Office said Johnson also spoke to Zarif and will meet Ali Akhbar Salehi, Iran's vice president and head of its nuclear agency, in London on Wednesday.
First, Congress could vote to snap sanctions back into place, or Trump could refuse to sign the next round of waivers for sanctions. Second, it appears that moderate Senate Republicans will side with Democrats to block passage of any sanctions that could endanger the Iran deal.
Why does U.S. President Donald Trump want to scrap it?
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.
What exactly that will look like is still being determined, but it could include greater congressional oversight.