A second round of sanctions targeting Iran's oil imports and energy and petrochemicals industries are scheduled to come into effect on 4 November. Since the U.S. withdrawal from the Iran deal, Iran's currency has taken a nosedive, soaring up to around 120,000 rials to a dollar.
Trump said this week he is willing to meet with Iran's leadership, without preconditions, "whenever they want" - a sharp departure from his threats against the regime last week.
The US has been unable to persuade China to cut Iranian oil imports, dealing a blow to President Donald Trump's efforts to isolate the Islamic Republic after his withdrawal from the 2015 nuclear accord.
He cited both internal Iranian politics making it hard for Tehran to cooperate with Trump and US politics making it hard for Trump to sell anything less than full success back home.
Over the weekend, Trump once again floated the idea of meeting, tweeting "I will meet, or not meet, it doesn't matter - it is up to them!"
The United States has told other countries they must halt imports of Iranian oil starting in early November or face US financial measures.
Sanctions against Iran will be strictly adhered to and act as long as the Iranian government will not change its course radically, said the US Secretary of state Mike Pompeo, reports the Associated Press. "They've got to behave like a normal country".
Starting this week, Washington will re-impose sanctions on Iran's purchases of US dollars, its trade in gold and precious metals, and its dealings with metals, coal and industrial-related software.
Unlike North Korea, with whom the Trump administration is now eager to negotiate, Iran never produced a nuclear bomb.
The exercise could shut down of the Strait of Hormuz, a crucial Gulf passage for shipments of numerous commodities.
Sporadic protests broke out in several cities in Iran for a fifth night on Saturday, a day after demonstrators attacked a Shiite seminary, according to Iranian news agencies and social media.
Earlier this week on Tuesday, hundreds of Iranians had rallied across the country, including Ahvaz, Isfahan, Karaj, and Shiraz in protest of growing economic difficulties, high inflation caused partly by the weak Rial.
Iran has also been hit by falling salaries set against the rising cost of living, while water shortages and power outages have also hit the embattled country.
The agency reported all protests had taken place without official permission and were subsequently broken up by police.
USA officials last week said Iran carried out a similar exercise, though Tehran did not immediately acknowledge it.