Listen to RFI's report
In 2015, through the Vienna nuclear agreement, Iran agreed to reduce uranium enrichment.
The next year most international sanctions against the country were lifted.
But US President Donald Trump felt this was a "bad deal".
His administration wants to force Tehran to stop its nuclear energy and ballistic missile programmes.and stop its support for conflicts in the Middle East.
So Washington imposed full-fledged sanctions on Iran's economy and oil trade on Monday.
Iran vows to bypass sanctions
Iran's President Hassan Rouhani reacted by saying that Iran would "proudly bypass sanctions" and continue to export its oil.
But Jamshid Assadi, a professor and researcher at the Burgundy School of Business, believes the contrary - that Iran will go into a recession.
"[The Iranian authorities] always say 'America will not be able to do anything against us'. But the economic situation is the worst it has ever been", he told RFI.
"The IMF has predicted a recession of 1.5 percent this year, and four percent next year," he added.
US sanctions may bring Iran closer to Asian partners
The US also said that it would impose sanctions on countries that do business with Iran.
However, eight countries, including Turkey, China, Japan South Korea and India, will be granted a waiver.
Even though the EU has condemned the US sanctions, saying it would set up a special financial system to do business with Iran, multinational companies like France's Total, Peugeot and Renault, as well as Germany's Siemens have been forced to leave Iran.
Mohammed Marandi, a political analyst at the University of Tehran, believes that this will actually bring Asian countries closer to Iran.
"The Europeans have been less resistant to the US than Asian powers," Marandi told RFI. "So we will see an increase in relations between Iran and Asia."
Marandi also believes that the murder of Saudi Arabian journalist Jamal Khashoggi is making more and more Asian partners move away from Saudi Arabia and look towards Iran.
"Countries like China do not want to put all their eggs in the Saudi or Emirati basket, so they're looking towards Iran", Marandi told RFI.
Ordinary Iranians 'terrified of future'
Meanwhile, students protested on the streets of Tehran on Monday, shouting "Death to America".
Sanam Shantyaei, France 24's specialist on Iran, says " a lot of ordinary Iranians are terrified about their future".
Shatyaei says that cutting off Iran from the rest of the world has an impact on food and medication supplied to the country.
She remembers when she went to Iran in 2015, in the aftermath of the nuclear deal under President Barack Obama.
"There was a real sense of hope, young people saying to me 'There will be job opportunities with European businesses flocking to Iran'. All that hope has evaporated".