The United States intends to fully enforce sanctions due to be reimposed against Iran early this week on orders from US President Donald Trump, Secretary of State Mike Pompeo says.
Washington's so-called "snapback" sanctions are due to be reinstated against Tehran on Tuesday, a US Treasury official said, speaking on condition anonymity.
Pompeo, speaking with reporters returning with him from an Asian trip on Sunday, said the White House will detail implementation of the measures on Monday morning.
"It's an important part of our efforts to push back against Iranian malign activity," he said.
"The United States is going to enforce these sanctions."
Despite opposition from European allies, Trump in May pulled the United States out of a 2015 deal between world powers and Tehran under which international sanctions were lifted in return for curbs on Iran's nuclear program.
Trump had denounced the deal reached under his White House predecessor, Barack Obama, as one-sided in Iran's favour.
Starting this week, Washington will reimpose 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.
The United States has told other countries they must halt imports of Iranian oil starting in early November or face US financial measures.
Iranian President Hassan Rouhani said last week that Trump's repudiation of the deal was illegal and Iran would not yield to Washington's renewed campaign to strangle Iran's vital oil exports.
Iran will ease foreign exchange rules, state TV reported on Sunday, in a bid to halt a collapse of the rial currency, which has lost half its value since April due to fears about the return of US sanctions.
Referring to recent sporadic protests in Iranian cities , Pompeo said: "The Iranian people are not happy - not with the Americans but with their own leadership. They're unhappy with the failure of their own leadership to deliver the economic promises that their leadership promised them."
Pompeo said the United States wants "the Iranian people to have a strong voice of who their leadership will be," although he stopped short of calling for regime change in Tehran.
He later said in a message on Twitter that the United States was "deeply concerned about reports of Iranian regime's violence against unarmed citizens" and urged respect for human rights.