The restoration of US sanctions on Monday targeting Iran's oil sales and banking sector is part of an effort by Trump to force Iran to halt its nuclear and ballistic missile programmes outright, as well as its support for proxy forces in conflicts across the Middle East.
"The effect of the initial sanctions is already being felt - the rial is at a low, Iran's economy is depressed and we're already seeing results on the ground", he added.
All of the other signatories - China, the European Union, France, Germany, Iran, Russia, and the United Kingdom - have remained in the deal despite the US action. "We also noted that the worldwide community is widely against unilateral sanctions", he told a daily news briefing in Beijing.
"In the next weeks all eyes will be on Iranian exports, whether there will be some cheating around United States sanctions, and on how quickly production will fall", said Riccardo Fabiani, an analyst for Energy Aspects.
Later a senior State Department official told reporters that the U.S. was ready for talks with Iran.
"America wanted to cut to zero Iran's oil sales. but we will continue to sell our oil.to break sanctions", Rouhani said. "We have the knowledge and the capability to manage the country's economic affairs", Foreign Ministry spokesperson Bahram Qasemi told state TV on Friday.
As part of the strategy to reduce dependence on Iran oil, state-owned oil companies like International Olympic Committee plan to use optional volumes built in their annual crude oil purchase contracts with suppliers like Saudi Arabia and Iraq - also to make up for any shortfall in supplies. "We have to stand to win." the president said. "The whole world understands these sanctions are real", he said during an interview of CBS's Face the Nation.
"But US bullying is backfiring. The US - and not Iran - is isolated", Zarif said in a tweet.
President Trump says that he wants to get Iran back to the negotiating table.
But proponents as well as the other parties to the deal - Britain, China, France, Germany, Russia, and the European Union - have vehemently defended it.
The sanctions end all the economic benefits America granted Tehran for its 2015 nuclear deal with world powers, though Iran for now continues to abide by the accord that saw it limit its enrichment of uranium.
Asked about it on "Fox News Sunday", Pompeo answered, "The Iranian banks that engage in sanctionable behavior will be sanctioned by the Department of Treasury, period, full stop".
Oil markets have been preparing for the sanctions for months.
Another said: "America is not our enemy, our enemies have taken us as hostages in our own home [country]".
"They're the strongest sanctions we've ever imposed", said President Donald Trump en route to a rally in Georgia on Sunday evening, hours before the sanctions on Iran's energy, shipbuilding and banking sectors kicked in at midnight.
The PM's official spokesman said: 'We regret the reimposition of sanctions by the US.
However, the United States is expected to give a short-term waiver to eight countries which could include India because of its commitment to significantly reduces the import of oil from Iran. But Brent crude was steady at $72.83 by 1230 GMT.
"SWIFT (will) be subject to U.S. sanctions if it provides financial messaging services to certain designated Iranian financial institutions".
United States sanctions against importers of Iranian oil threaten the crude oil market's precarious balance and risk surging prices, all under Saudi Arabia's watchful gaze, according to experts.
Former New York Times reporter Michael Gordon, now with the Wall Street Journal, reports on the related reorientation of American foreign policy in "Trump digs in for a long cold war with Iran" (accessible here via Outline).