The US will impose "major" additional sanctions on Iran in a bid to prevent the country obtaining nuclear weapons, President Donald Trump says.
He said economic pressure would be maintained unless the leadership in Tehran changed course.
"We're putting additional sanctions on," he told reporters. "In [some] cases we are moving rapidly."
It comes after Iran announced it would exceed internationally agreed limits on its nuclear programme.
The limit on its stockpile of enriched uranium was set under a 2015 nuclear deal with world powers. In return, relevant sanctions were lifted, allowing Iran to resume oil exports - the government's main source of revenue.
Iran has responded by scaling back its commitments under the nuclear deal.
The reinstatement of US sanctions last year - particularly those imposed on the energy, shipping and financial sectors - caused foreign investment to dry up and hit oil exports.
The sanctions bar US companies from trading with Iran, but also with foreign firms or countries that are dealing with Iran.
This has led to shortages of imported goods and products that are made with raw materials from abroad, most notably babies' nappies.
The plunging value of the rial has also affected the cost of locally produced staples such as meat and eggs, which have soared in price.
Iran has responded to the economic pressure by violating some of the nuclear deal's commitments. It has also accused European countries of failing to live up to their promises of protecting Iran's economy from US sanctions.
He said economic pressure would be maintained unless the leadership in Tehran changed course.
"We're putting additional sanctions on," he told reporters. "In [some] cases we are moving rapidly."
It comes after Iran announced it would exceed internationally agreed limits on its nuclear programme.
The limit on its stockpile of enriched uranium was set under a 2015 nuclear deal with world powers. In return, relevant sanctions were lifted, allowing Iran to resume oil exports - the government's main source of revenue.
Iran has responded by scaling back its commitments under the nuclear deal.
The reinstatement of US sanctions last year - particularly those imposed on the energy, shipping and financial sectors - caused foreign investment to dry up and hit oil exports.
The sanctions bar US companies from trading with Iran, but also with foreign firms or countries that are dealing with Iran.
This has led to shortages of imported goods and products that are made with raw materials from abroad, most notably babies' nappies.
The plunging value of the rial has also affected the cost of locally produced staples such as meat and eggs, which have soared in price.
Iran has responded to the economic pressure by violating some of the nuclear deal's commitments. It has also accused European countries of failing to live up to their promises of protecting Iran's economy from US sanctions.

