New U.S. sanctions imposed on Iran on Monday target Supreme Leader Ayatollah Ali Khamenei and senior military leaders of the Islamic republic.
President Donald Trump slapped the sanctions on Tehran for what he described as its "aggressive behavior" including the shooting down of U.S. drone.
The White House said the sanctions "will deny Iran's leadership access to financial resources, blocking them from using the United States financial system or accessing any assets in the United States."
In addition to Khamenei, the US Treasury Department said it was taking action against eight senior commanders of the Islamic Revolutionary Guards Corps (IRGC).
"These commanders sit atop a bureaucracy that supervises the IRGC's malicious regional activities, including its provocative ballistic missile program, harassment and sabotage of commercial vessels in international waters, and its destabilizing presence in Syria," the Treasury Department said.
Treasury Secretary Steven Mnuchin said the United States will also blacklist Iranian Foreign Minister Mohammad Javad Zarif and block "billions" more in Iranian assets.
"This action is a warning to officials at all levels of the IRGC and the rest of the Iranian regime that we will continue to sanction those who export violence, sabotage, and terrorism," Mnuchin said.
The new sanctions build on a series of previous ones imposed by the United States over the past few months in a bid to isolate the Islamic republic.
In November, six months after Trump withdrew from the nuclear deal with Iran, the United States took aim at its oil exports and financial transactions.
Specific actions targeted Iran's banking, shipping and energy sectors, threatening penalties against companies, even those of US allies in Europe and elsewhere, who do business in them.
According to the Bloomberg news agency, Iranian oil exports have fallen from 1.5 million barrels per day in October 2018 to 750,000 bpd in April.
In May, in a bid to further choke off oil exports, Iran's top foreign exchange earner, the United States lifted exemptions granted to eight countries, including Turkey and India, allowing them to purchase Iranian oil.
- Punitive measures -
The sanctions last year brought back punitive measures that were imposed and then lifted by former president Barack Obama, who reached an international agreement under which Iran moved to end its nuclear program.
On August 7, 2018, the first sanctions lifted under the 2015 nuclear deal came into force, banning:
- The Iranian government's purchases of dollars, or the international buying and selling of significant sums of rials, Iran's currency under pressure
- Purchases of Iranian treasury bonds
- Trade in gold or other precious metals, aluminum, steel, carbon or graphite
- Automobile and commercial aviation trade
- US imports of Iranian carpets or foodstuffs
Under the sanctions, any foreign institution that does business with Iran's central bank or other banks in the country loses access to the US financial system.
The risks for foreign banks are high in a globalized economy in which the dollar remains the dominant currency.
The United States has also sought to cut off Iranian access to SWIFT, the international system of interbank transfers.