As of Monday, the Trump administration has reinstated all sanctions on Iran that were lifted under the 2015 nuclear deal.
Sanctions on Iran's energy, shipbuilding, shipping and bank sectors snapped back into place at midnight.
While speaking during a cabinet meeting Monday, Iranian President Hassan Rouhani reportedly vowed to "proudly break the unjust sanctions."
President Donald Trump announced earlier this year that he was pulling the U.S. out of the 2015 Iran nuclear deal — which put restrictions on Iran's nuclear program in return for relief from economic sanctions.
The president's decision allowed U.S. sanctions against Iran to, over time, snap back into place. The first round was reimposed back in August and affected Iran's trade in gold and other precious metals, its automotive sector and its purchases of U.S. dollars.
The Trump administration is letting eight so-called "jurisdictions" temporarily continue to import Iranian oil despite the sanctions going back into effect. Those countries are China, India, Italy, Greece, Japan, South Korea, Taiwan and Turkey.
Additional reporting from Newsy affiliate CNN.