Iran has said it is confident it can counter widened US sanctions after Washington announced what it described as an "economic D-Day" against the country to try to isolate it from the global economy.
Iranian Economy Minister Ali Madanizadeh said Tehran was "fully prepared" for the sanctions, which he said would lead to "another defeat" for the US.
Announcing a raft of new measures, US Treasury Secretary Scott Bessent said any nation financially partnering with Iran would be isolated, and that banks and businesses dealing with Iran would share its isolation if they refused to cut ties.
The moves follow U-turns and extended deadlines from the White House in its efforts to end the conflict.
Bessent described the measures as "the single greatest financial offensive ever" against Iran, which would "tighten the noose and block every potential source of revenue".
Some economists have questioned whether the latest sanctions will be effective, as this depends on the reaction from Iran's trading partners.
These include China, the biggest buyer of Iranian oil, which has ignored previous US sanctions and continued to do business with Tehran.
Last week, another of Iran's trade partners, the United Arab Emirates, said it was halting all financial transactions with the country.
But hours after the US announcement, Iran said it was confident it would continue to trade with other nations.
Madanizadeh said neither China nor Russia had accepted the US measures, and predicted other countries would resist them.
"The government is and was ready and has a two-year plan to manage these events," he told state television, adding Tehran had been "waiting for these plans for a long time".
"We also have our own tools and know how to play the game," he said.
Responding to the US announcement, China said it was firmly opposed to what it called "illegal unilateral sanctions".
Foreign ministry spokesman Lin Jiang said economic pressure tactics would not help resolve problems, and Beijing would safeguard its own interests.
The war has led to hikes in global oil prices, and in response to the latest threat Iran warned it would shut down all oil exports from the region if the war continued.
The Iranian regime has also issued a fresh warning to ships not to pass through the Strait of Hormuz without permission, according to Reuters.
One fifth of the world's oil and gas usually passes through the strait - a narrow waterway south of Iran. But the flow has been effectively blocked by the country since the conflict began at the end of February, leading to higher oil prices globally.
At a press conference earlier on Monday outlining what has been called "Operation Economic Outcast", Bessent said the US was launching an "economic onslaught against Iran's financial connections around the globe".
"Iran now faces a very clear choice with only two paths before them: complete global isolation... or a path back to normalcy with an opportunity to rejoin the global economy," he said.
The treasury secretary claimed America was "no longer managing the Iranian threat, we are ending it".
Bessent said the Treasury had mapped networks, facilitators and financial channels used by Iran to evade sanctions to trade oil.
The department said it had issued determinations against five sectors: digital assets, technology, gold, aviation and shipping. The Treasury has also imposed sanctions on almost 60 entities, individuals and vessels.
In a warning to governments and entities assisting or trading with Iran, he said they could not "claim they are blind to enabling this activity".
He declined to highlight specific countries, but said Trump would be phoning world leaders "with specific requests to cease their interactions with the regime".
While he said it was important to give people time to understand the new sanctions, he added: "They should know that we will move very quickly and that we are serious."
David Oxley, chief climate and commodities economist at Capital Economics, cast doubt on the effectiveness of the sanctions announcement.
"With the renewed US naval blockade already strangling Iran's oil exports, the direct impact of 'economic D-Day' on Iran's energy revenues will be somewhat of a damp squib," he said.
"We suspect that the new package will have only a limited direct impact on Iranian energy flows in the short term."
He said that was partly due to the fact roughly 90% of Iran's oil goes to China, a country "which has not recognised US sanctions in the past and is unlikely to be cowed this time either".
"Generally, the Chinese are against unilateral sanctions," said Ali Vaez, deputy director of the Middle East and North Africa Program at the International Crisis Group.
"They would comply with multilateral or international sanctions, but unilateral sanctions just imposed by the US - they have always seen that as illegitimate," he told BBC Radio 4's Today programme.
And although Iran's neighbours like Pakistan, Turkey and Iraq want to maintain good relationships with the US, they "can't really afford to cut off ties with Iran", Vaez added.
He said putting economic pressure on Tehran "doesn't work" because the Iranian regime is willing to "absorb any pain" and pass that onto its people.
Over the course of the conflict so far, previous threats have included Trump saying in April that "a whole civilisation will die tonight" unless Iran agreed a deal to end the war and unblock the Strait of Hormuz.
The US eventually climbed down from that position after mediator Pakistan intervened and called for more diplomacy.
The economic impact of the Iran war is being felt in the US and across the world. Higher oil prices have fuelled concerns over the cost of living, with petrol and diesel prices much higher than they were a year ago.
In the US, gasoline prices have surpassed $4 a gallon and affordability is among the top concerns of American voters ahead of the mid-term elections in November.
On Monday, a barrel of Brent crude, the global benchmark for oil prices, was $92.
Last week, Bessent announced the US government would intervene in the bond markets and buy back more government debt in a bid to boost demand for bonds and lower borrowing rates.
But the impact of the announcement was short-lived, with long-term borrowing costs bouncing back up a day later.
