Video report by ITV News Correspondent Emma Murphy
Tensions between Iran and the United States continue to rise after Tehran threatened to enrich its stockpile of uranium.
Donald Trump has spoken out against Iran by announcing new sanctions against the country - imposing restrictions on Iranian steel, aluminium, copper and iron.
These sectors provide Iran's troubled economy with foreign currency earnings.
The US President said Tehran could expect "further actions unless it fundamentally alters its conduct".
The White House said it would continue its "maximum pressure" campaign on the Iranian government until it stops supporting terror groups, ends destabilising activities in the region and gives up any nuclear weapons efforts.
"We call on the regime to abandon its nuclear ambitions, change its destructive behaviour, respect the rights of its people, and return in good faith to the negotiating table," Mr Trump said.
The United States, Germany, Britain, France, Russia, China and the European Union signed a deal with Iran in 2015 which lifted international sanctions in exchange for Tehran limiting its nuclear programme.
One year ago, Mr Trump pulled out of the agreement, which he called "the worst deal in history".
He said the accord should also have restrained Iran's ballistic missile programme and curbed what his administration considers Tehran's malign activities in the region.
Iran threatened on Wednesday to enrich its uranium stockpile closer to weapons-grade levels in 60 days if world powers fail to negotiate new terms for its 2015 nuclear deal.
Iran has stopped its sale of excess uranium and heavy water as a first step - something required under the deal.
In 60 days, if no new deal is in place, Iran said it would increase its enrichment of uranium beyond 3.67%, which is permitted by the accord.
President Hassan Rouhani did not say how far Iran would be willing to enrich, although the head of its nuclear programme again reiterated Iran could reach 20% enrichment within four days.