Mike Pompeo, the US secretary of state, threatened Iran with the "strongest sanctions in history" and vowed to "crush" the regime’s proxies around the world on Monday, sparking a furious response from Tehran.
Mr Pompeo also called for a new nuclear treaty with Iran to replace the Obama-era deal that Donald Trump withdrew from earlier this month.
But the top US diplomat issued a list of 12 requirements for such a deal, many of which Iran would be unlikely to agree to.
He said the US would apply "unprecedented financial pressure" on Iran and send teams of specialists to allies around the world to explain US policy.
Mr Pompeo said if Iran makes "major changes" the US was willing to lift all sanctions.
He framed the 2015 deal as allowing Iran to increase its malign influence across the Middle East on the back of funding from renewed trade with the West.
Mr Pompeo accused the Iranian regime of "playing with house money that has become blood money". And he told the regime: "Understand your current activities will be met with steely resolve".
He added: "The Obama administration made a bet. That bet was a loser with massive repercussions.
"The bet was a bad one for the US, for Europe, and for the world. Iran’s leaders saw it as a starting gun for the march across the Middle East."
He added: "We will track down Iranian operatives and their proxies around the world and we will crush them."
America ‘open’ to a new deal
Mr Pompeo called for a new treaty with Iran, ratified by Congress, that ends enrichment and gives inspectors access .
He said Iran must "stop enrichment" of uranium, which was allowed within strict limitations under the 2015 deal.
Iran must also allow nuclear inspectors "unqualified access to all sites throughout the country".
The Iranians must also declare all previous efforts to build a nuclear weapon, he said.
Mr Pompeo also demanded that Iran must end support for Shiite Houthi rebels in Yemen, withdraw all forces from Syria, halt support for Hezbollah and stop threatening Israel.
It must also release all US citizens missing in Iran or being held on "spurious charges".
Mike Pompeo Iran demands
Mr Pompeo said if Iran made "major changes" the US would be willing to lift all sanctions, restoring full diplomatic and commercial ties.
The US. would even support the modernisation of Iran’s economy and help it reintegrate into the global financial system, he said.
He added: "A treaty would be our preferred way to go."
The future of the 2015 deal remains in the balance, with Iran saying it will only keep to the agreement if the economic benefits gained from it remain in placed.
American allies have been clamouring for the Trump administration to explain its ‘Plan B’ approach to Iran after unilaterally quitting the deal.
US ‘fully prepared’ to respond if Iran resumes nuclear programme
Mr Pompeo said the US was ready if Iran chose to resume its nuclear programme.
He said: "Our demands on Iran are not unreasonable – give up your programme.
"Should they choose to go back, should they begin to enrich, we are fully prepared to respond to that as well. I hope they will make a different decision, choose a different path."
He did not say what the US response would be.
European businesses would have to cut ties with Iran
Much of the effectiveness of the Trump administration’s reimposition of sanctions depends on European businesses cutting economic ties with Iran.
Firms in the EU have taken much more advantage of the 2015 waiving of sanctions to sign contracts increasing business in Iran than those in America.
The EU exported over €10.8 billion (£9.4 billion) worth of goods to Iran in 2017, half of which was made up by machinery and transport. That is up from €6.5 billion (£5.7 billion) in 2015.
In return the EU has moved to reimpose a “blocking statue” originally meant to circumvent a the US embargo against Cuba in the 1990s that would protect European businesses.
Click Here: Rugby league Jerseys