In May, US President Donald Trump pulled Washington out of world powers' 2015 nuclear deal with Iran and reimposed a first round of sanctions on Iran in August. Contrary to what he called "fueled misinformation", he stated that SWIFT, "if it provides financial messaging services to certain designated Iranian financial institutions...could be subject to sanctions". The president did not respond to a question about the waiver. "We have to stand to win." the president said.
"India said to the United States that they can't stop before March, they are facing a major currency crisis", explained Joel Hancock, analyst at Natixis.
The European Union has established a mechanism to permit its multinational companies to maintain presences in Iran, but all signs are that the U.S. sanctions will be dissuasive.
In addition, the Brussels-based Swift network for making global payments is expected to cut off links with targeted Iranian institutions, isolating Iran from the worldwide financial system.
USA secretary of state Mike Pompeo has said the Trump administration is committed to reducing Iranian crude imports by its major buyers China and India to "zero" and warned ominously, but without specifics, "watch what we do".
India and China are among them, according to officials, but an announcement is expected on Monday.
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In the capital city of Tehran, the rally was held at the venue of the former United States embassy, which is known by Iranians as the "Den of Espionage".
The renewed sanctions are designed "to paralyse the (Iran's) economy and keep it backwards".
"These sanctions have already had an enormous impact", Pompeo said, adding that Trump's policy will be "fully in place" as of Monday.
Rouhani separately said leaders from "four powers" met with Iran on the sidelines of the September meeting of the United Nations General Assembly to try to save the deal, including brokering a possible meeting with Trump.
What has the reaction been in Iran?
The crowd chanted "Down with the US", and 'Death to Israel' during today's rally in the capital, while similar demonstrations were held in other cities and towns.
The demonstrations took place on the 39th anniversary of the occupation of the U.S. embassy in Tehran, which led to four decades of mutual hostility.
Iran greeted the re-imposition of US sanctions on Monday with air defense drills and an acknowledgement from President Hassan Rouhani the nation faces a "war situation", raising Mideast tensions as America's maximalist approach to the Islamic Republic takes hold.
Hardliners hold protests to commemorate the siege every year but on Sunday, protestors also vented their fury about the sanctions.