As a candidate on the presidential campaign trail last year, Mr Trump repeatedly criticised the Joint Comprehensive Plan of Action, pledging to rip up the Iranian nuclear deal – an agreement which curbed Iran’s nuclear program in return for massive sanctions relief.
As President that criticism has continued, culminating in his address to the United Nations General Assembly last month when he described the deal as an embarrassment to the US.
While the President could announce later today that he is withdrawing the US from the pact, that is unlikely as it would have significant international consequences.
It is more likely that President Trump will refuse to certify that Iran is in compliance with the terms of the deal.
Doing that would then require Congress to consider what course of action to pursue, but the deal itself would remain intact pending that review.
Mr Trump could decide to impose further sanctions on Iran, but that would be tantamount to collapsing the deal and is also unlikely at this stage.
US Secretary of State Rex Tillerson spent much of this week on the telephone, talking through a decision that is deeply unpopular with allies.
So, while US officials still insist that “America First” does not mean “America Alone,” on this issue they are starkly isolated. The other signatories all back the deal.
“This is the worst deal. We got nothing,” Mr Trump thundered to Fox News on Wednesday. “We did it out of weakness when actually, we have great strength.”
“It will be absolutely clear which is the lawless government. It will be clear which country is respected by the nations of the world and global public opinion,” he added.