Western nations say Iran aims to build nuclear weapons.
"Treasury's imposition of unprecedented financial pressure on Iran should make clear to the Iranian regime that they will face mounting financial isolation and economic stagnation until they fundamentally change their destabilizing behavior", said Treasury Secretary Steven Mnuchin in a statement.
In particular the sanctions target Iran's vital energy sector and its shipping and shipbuilding sector and banking sector. The visiting envoy also called for concreted action by the global community to stand against U.S. unilateralism, and denounced the use of economic and trade options for imposing a country's political will on others.
Eight countries will benefit, however, an exemption for the oil, including Turkey, and possibly China and India. The move, which is aimed at pressuring Iran to curb its nuclear programme, brings the total number of entities facing the wrath of America to 900.
But for the first time, the United States targeted Iran Air.
Five of the eight economies granted waivers as long as they work to reduce oil imports from Iran to zero are in Asia: China, India, Japan, South Korea and Taiwan.
Iran's health sector is concerned about the impact of the sanctions, for example lives will be at risk when the country's supply of medicine runs out due to the sanctions. "Today the enemy (the United States) is targeting our economy. the main target of sanctions is our people", Rouhani said. "We have the toughest sanctions ever imposed, but on oil we want to go a little bit slower because I don't want to drive (up) the oil prices in the world", he told reporters before flying to a campaign event. "And as far as the U.S. is concerned, they are well aware about our expectations of the requirement which we have for oil domestically and which is very critical for sustaining our economic growth".
Iranian officials expressed their gratitude for South Korea's prior consultations on the sensitive issue, the source said.
Americans cast votes on Tuesday to decide whether Donald Trump's Republicans maintain their grip on the US Congress, or if.
All of the other signatories, China, the European Union, France, Germany, Iran, Russia and the United Kingdom, have remained in the deal despite U.S. action.
Oil prices rallied above $85 per barrel in October on fears of a steep decline in Iranian exports.
The reinstated sanctions follow the Trump administration's decision in May to pull out of the worldwide nuclear deal.
South Korea said on November 5 it has been granted a waiver to at least temporarily continue to import condensate, a super-light form of crude oil, from Iran and also still continue financial transactions with the Middle East country.
Oil prices rose as the sanctions went into effect, with worldwide benchmark Brent crude up by more than $1 to a session high of $73.92 a barrel.
U.S. West Texas Intermediate (WTI) crude futures CLc1 were at $62.86 a barrel at 0800 GMT, down 24 cents, or 0.4 percent, from their last settlement. However, news of the waivers last week sent prices lower as top buyers would continue to import Iranian oil.