The move will restore USA sanctions that were lifted under a 2015 nuclear deal negotiated by the administration of President Barack Obama, and add 300 new designations in Iran's oil, shipping, insurance and banking sectors.
After initially promising to drive the country to zero exports of oil, the USA has offered a waiver to eight buyers of Iranian crude, a move that Secretary of State Mike Pompeo defended yesterday.
Senator Marco Rubio of the Senate Foreign Relations Committee responded to the administration's announcement, specifically noting the SWIFT transactions issues as well as the issuance of SREs: "More must be done to press the SWIFT financial messaging service to once again sever connections with the Central Bank of Iran and other sanctioned Iranian banks by a certain date".
Tehran -Iran´s annual rally to mark the storming of the U.S. embassy and hostage-taking of 1979 had particular significance on Sunday on the eve of renewed sanctions by Washington.
General Mohammad Ali Jafari, the commander-in-chief of Iran's paramilitary Revolutionary Guard, gave a speech vowing that Iran "can overcome this economic war and failure of the sanctions project is imminent".
While the commemoration annually sees American flags burned and cries of "Death to America" rise up, it also has a carnival-like atmosphere for the students and others taking part.
Before travelling to a campaign rally for the USA midterm elections, President Trump said Iran was already struggling under his administration's policies.
All of the other signatories - China, the European Union, France, Germany, Iran, Russia, and the United Kingdom - have remained in the deal despite the USA action.
If the USA had not granted waivers to China and some of the other countries, they would have also ignored the sanctions.
"Even if the United States grants exemptions, Washington will demand that the volume imported from Iran be significantly reduced", said UBS analyst Giovanni Staunovo, who expects prices to rise.
Part of the explanation lies in the ambiguous position of the United States, which initially insisted that the sanctions were created to reduce Iranian exports to zero barrels, but has since has softened its position.
Iranian state media said millions turned out in towns and cities, swearing allegiance to the Supreme Leader Ayatollah Ali Khamenei, although the BBC was unable to independently verify this figure.
Crude oil markets topped out with WTI reaching 75.00 per barrel only a month ago, but a crushing wave of crude production is threatening global oil markets' two-year bullish extension.
The Trump administration is restoring all sanctions lifted under the 2015 nuclear deal in a bid to pressure Iran.
Some 52 Americans were held hostage for 444 days in Iran.
Iran's economic chaos sparked mass anti-government protests at the end of past year which resulted in almost 5,000 reported arrests and at least 25 people being killed.