US Treasury Secretary Scott Bessent laid out plans for the "economic asphyxiation" of Iran, expanding Washington's secondary sanctions threats and warning of dire consequences for countries that decline to join the pressure campaign.
Mr Bessent's address comes almost six months into a war on Iran that has ground to a stalemate, with stalled peace talks and Iran preventing most traffic through the crucial Strait of Hormuz.
"Around the globe, our objective is to sever every economic lifeline that sustains this tyrannical regime until Tehran stands alone," Mr Bessent told a press conference.
He added: "We are going to hold everyone accountable, and this is economic asphyxiation of this regime. We are launching an economic onslaught against Iran's financial connections around the globe."
Watch: US sanctions on Iran 'economic asphyxiation' - Bessent
The US Treasury Department said it has mapped the networks, facilitators, and financial channels that Iran uses to smuggle oil and evade sanctions.
It added that Washington would be working with US partners to target any source of Iran's "illicit revenue".
Mr Bessent said that countries not joining US sanctions would "share in the isolation" of Iran.
He noted that US President Donald Trump is making phone calls to world leaders with requests to stop their interactions with Tehran.
Iranian foreign ministry spokesman Esmaeil Baqaei said taking part would "definitely have its own consequences".
The Treasury Department said that it has "issued determinations against five critical sectors - digital assets, technology, gold, aviation, and shipping - that the Iranian regime uses to try to prop up its failing economy".
Mr Bessent, meanwhile, vowed that any entity "that facilitates money laundering on behalf of Iran will be removed from the US dollar system".
Asked if Chinese banks dealing with Iran could be targeted, Mr Bessent said "no one is above the reach of US sanctions".
The Treasury chief earlier declared that an "economic D-Day" had begun against Iran, in a column for the Financial Times.
The United States and Israel triggered the Middle East war with a massive wave of bombing against Iran on 28 February, sparking Iranian retaliation across the region.
Oil exports plunge
The US naval blockade of Iran has seen its oil exports via the Strait of Hormuz fall from two million barrels a day pre-war to just 0.4 million by mid-August, according to maritime tracker Kpler.
Meanwhile, the country has been under crushing international sanctions for decades, with a brief period of easing under a 2015 nuclear deal that Mr Trump later ripped up as part of a "maximum pressure" campaign.
The Islamic republic has weathered those efforts and, before the war, continued to export millions of barrels of oil, mostly to China, and evade sanctions through complex international financial networks.
For ordinary Iranians, the standoff is likely to bring only more economic pain after years of rampant inflation, which in December and January fuelled massive anti-government protests.
Sarah Hassanbeigi, a 32-year-old pharmacist in Tehran, put it simply: "It's really very difficult. I don't think people can really take this much longer."
Yesterday, Iranian President Masoud Pezeshkian admitted that Iran faced "many problems in society".
"We are striving with all our hearts to overcome inflation, livelihood problems, unemployment, and to secure the future of the people, so that they can live with dignity and pride," Mr Pezeshkian said.
Delegation from Pakistan
Last week, the Iranian president, considered a relative moderate, said Tehran should "bring the war to an end now as we are in a position of power and dignity".
That followed supreme leader Mojtaba Khamenei appointing hardliners to key security positions.
Ms Hassanbeigi said she wanted peace. "Naturally, negotiations mean that both sides have to compromise. My personal opinion is that Iran should compromise now," she told AFP.
Throughout the war, diplomatic efforts, pushed on by mediators, have sought a negotiated end to the conflict.
Today, Pakistan's army chief was expected in Iran. Islamabad was a leading mediator in talks that helped secure an April ceasefire that later fell apart.
Omani Foreign Minister Badr al-Busaidi was also due in Iran tomorrow, as Muscat and Tehran seek a deal on regulating passage through Hormuz.