Al-Jazeera - Iran��will continue to find international buyers for its oil and use the Strait of Hormuz to transport it, the country's foreign minister�said,�warning that if the�United States�tries to stop Tehran it should "be prepared for the consequences".

Speakingin New York City on Wednesday,�Foreign Minister�Mohammad�Javad Zarif cautioned US President�Donald Trump's administration against taking the "crazy measure" of attempting to block Iranian oil sales.

Zarif also said it was in the Islamic Republic's "vital national security interest" to keep the Gulf and Strait of Hormuz open.

The Strait of Hormuz is a major oil shipment channel in the Gulf.

Zarif's comments at an Asia Society event came after Washington on Monday�announced�it was ending waivers that have allowed some of Iran's largest oil customers to import fuel from the Islamic Republic in limited volumes without facing financial penalties from the US.

The move means buyers must stop purchases by May or face sanctions, the White House said. It is aimed at bringing "Iran's oil exports to zero" to deny Tehran "its principal source of revenue".

The White House�said�the US,�Saudi Arabia�and the�United Arab Emirates�were�working to "ensure that supplies are made available to replace all Iranian oil removed from the market".

Following the announcement, oil prices hit their highest level since November, on Tuesday.

'Economic terrorism'

Washington reimposed oil sanctions on Iran in November of last year, six months after Trump�withdrew�the US from the landmark 2015 Iran nuclear deal, which�had given the Islamic Republic sanctions relief in exchange for curbs on its nuclear programme.

Eight countries -�China, India, South Korea,�Japan, Taiwan, Turkey,�Italyand Greece - were given a six-month reprieve from the measures.

Turkey slammed the US move to withdraw the waivers, with Foreign�Minister Mevlut Cavusoglu saying it would "harm Iranian people".

Iran, meanwhile, denounced the oil sanctions as "illegal" and accused the US of committing "economic terrorism".

Supreme Leader Ayatollah Ali Khamenei said on Wednesday that "Iranians won't give in" despite Washington's attempts to ratchet up pressure on Tehran.

"They wishfully think they have blocked Iran oil sales, but our vigorous nation and vigilant officials, if they work hard, will open many blockades," Khamenei said in a speech, excerpts of which were broadcast on state television.

Tensions between Tehran and Washington escalated earlier this month after Trump's administration designated the Islamic Republic's elite Revolutionary Guard Corps (IRGC) a "foreign terrorist organisation",�drawing�a swift tit-for-tat response from Iran.

The White House decision�marked an unprecedented step by the US against an entire institution of a foreign government.

Trump said the move�"underscores the fact that Iran's actions are fundamentally different from those of other governments" and vowed to continue increasing financial pressure on Tehran until "it abandons its malign and outlaw behaviour".

The US president's administration has already put sanctions in place on more than 970�Iranian individuals and entities, according to the US State Department.

Prisoner swap

On Wednesday, Zarif said Washington's sustained pressure campaign on Tehran showed the "B team wants regime change", referring to Trump-ally Israeli Prime Minister�Benjamin�Netanyahu�and US�National Security Adviser�John Bolton, a staunch critic of Iran's leadership.

"It is not a crisis yet, but it is a dangerous situation," he told the event in New York.

But Zarif also suggested possible cooperation with Washington to bring stability to Iraq and Afghanistan, and said Tehran was open to negotiating a prisoner swap deal, pointing specifically to the case of�British-Iranian aid worker�Nazanin Zaghari-Ratcliffe.

Ratcliffe, who�has been�held�in Iran since 2016, could be swapped for an Iranian woman currently held in Australia for the past three years on a US extradition request, Zarif said.

"Let's have an exchange. I'm ready to do it and I have authority to do it," he added.