Speaking during a trip to New Zealand Ms Mogherini dramatically urged European companies to “increase business with and in Iran”.
This ignores a warning from Trump that: “Anyone doing business with Iran will not be doing business with the United States.”
A new set of US sanctions on Iran came into effect yesterday morning at 05.01 UK time.
They will primarily effect Iran’s ability to acquire US currency as well as many metals.
This follows Trump’s decision to pull the US out of the Iran nuclear deal, designed to restrict the country’s nuclear programme, in May this year.
Trump claimed it was a “horrible one-sided deal that should never, ever have been made” which failed to stop the development of Iranian missiles or Iran backing terror groups across the middle east.
The European Union, as well as Russia, China, the UK, Germany and France continue to support the deal.
Ms Mogherini said: “We are doing our best to keep Iran in the deal.
“To keep Iran benefiting from the economic benefits that the agreement brings to the people of Iran, because we believe this is in the security interests of not only our region but also of the world.
“If there is one piece of international agreements on nuclear non-proliferation that is delivering, it has to be maintained.
German car and truck dealer Daimler AG said on Thursday that it would end involvement in Iran, ending plans to start making trucks in the country.
UK Foreign Office minister Alastair Burt told the BBC than the “Americans have really not got this right”.
He added that the UK thinks the nuclear deal is crucial “not only to the region’s security but the world’s security”.
The EU has imposed a ‘blocking statute’ which means European companies could be sued if them comply with US sanctions and may be able to sue the US for interference if they don’t.
However its effectiveness has already been questioned by many experts.
In an official statement the Trump administration said: “we urge all nations to take such steps to make clear that the Iranian regime faces a choice.
“Either change its threatening, destabilising behaviour and reintegrate with the global economy or continue down a path of economic isolation.”