The EU's foreign policy chief, Federica Mogherini, commenting on possible unprecedented sanctions against Iran pledged by US Secretary of State Mike Pompeo, has warned that there is "no alternative" to the Joint Comprehensive Plan of Action, also known as the Iran nuclear deal.

Mogherini issued a statement on Monday, saying: "Secretary Pompeo's speech has not demonstrated how walking away from the JCPOA (nuclear deal) has made or will make the region safer from the threat of nuclear proliferation or how it puts us in a better position to influence Iran's conduct in areas outside the scope of JCPOA."

Earlier in the day, Pompeo said that Washington would increase financial pressure on Iran by imposing the "strongest sanctions in history" on the Islamic Republic if Tehran refuses to change the course of its foreign and domestic policy.

The Iranian Foreign Ministry also released a statement condemning Pompeo's remarks, stressing that the US has no right to interfere in Iran’s internal affairs.     

The foreign ministry statement said:  "Iran rejects the allegations and lies in this so-called new strategy and condemns the US Secretary of State's ... open interference in its internal affairs and the unlawful threats against a United Nations member state."