US President Donald Trump has issued a strong warning to anyone trading with Iran, following his re-imposition of sanctions on the country.
"Anyone doing business with Iran will NOT be doing business with the United States," the president tweeted.
Some re-imposed sanctions took effect overnight and tougher ones relating to oil exports will begin in November, reports BBC.
Iran's president said the measures were "psychological warfare" which aimed to "sow division among Iranians".
The sanctions follow the US withdrawal from the Joint Comprehensive Plan of Action, also known as the Iran nuclear deal, earlier this year.
The deal, negotiated during the presidency of Barack Obama, saw Iran limit its controversial nuclear activities in exchange for sanctions relief.
Mr Trump has called the deal "one-sided", "disastrous" and the "worst I've ever seen". He believes renewed economic pressure will force Iran to agree to a new deal.
The European Union, which remains committed to the original agreement, has spoken out against the sanctions, vowing to protect firms doing "legitimate business" with Iran.
What else did Mr Trump say in his latest tweet?
He praised the "most biting sanctions ever imposed" and said they would "ratchet up to another level" in November.
"I am asking for WORLD PEACE, nothing less!" he said.
On Monday he had said that Iran faced a choice to "either change its threatening, destabilising behaviour and reintegrate with the global economy, or continue down a path of economic isolation".
"I remain open to reaching a more comprehensive deal that addresses the full range of the regime's malign activities, including its ballistic missile programme and its support for terrorism," he said.