On Tuesday, US President Donald Trump announced he was pulling out of a landmark deal curbing Iran's nuclear program and reintroducing sanctions on the Islamic republic and those who trade with it.

The decision overturned years of painstaking diplomacy and left European allies scrambling to save the hard-fought deal.

Washington has given European firms doing business in Iran up to six months to wind up investments or risk US sanctions and they are also forbidden from signing any new contracts with Iran.

On Thursday France's top diplomat Jean-Yves Le Drian slammed those conditions, saying Washington needed to negotiate with its European allies on any sanctions that might affect their companies.

"We feel that the extraterritoriality of their sanction measures are unacceptable," he told the French daily Le Parisien.

"The Europeans should not have to pay for the withdrawal of an agreement by the United States, to which they had themselves contributed," he said.

Europeans, he added, would "do everything to protect the interests of their companies" and planned to lead "tight negotiations" with Washington via the European Union.

Trump's decision to pull out of the Iran deal has left his country diplomatically isolated.

Tehran agreed in 2015 to curb its uranium enrichment programme in exchange for sanctions relief after mammoth negotiations with the US, France, Germany, the United Kingdom, China and Russia.

All the other signatories to the deal had called on Trump to stay with the agreement and condemned his decision to leave -- although Le Drian's criticisms are some of the most forceful yet from a key European ally.