The European Union's 27 member states "decided to take the necessary steps to maintain the restrictive measures under the EU non-proliferation regime on Iran," a statement said.

The deal agreed with world powers in 2015 was aimed at curbing Iran's nuclear programme in exchange for the lifting of international sanctions.

But the accord began unravelling in 2018 when then US president Donald Trump unilaterally withdrew from it and began reimposing sanctions and Iran retaliated by dropping some of its obligations under the agreement.

The decision to keep the sanctions in place was originally announced by Britain, France, and Germany, all signatories to the pact, last month.

Tehran has already warned the EU that the move was "illegal".

The sanctions remaining in place include blacklisting missile manufacturers and affiliates of Iran's Revolutionary Guards.

The EU serves as a mediator in efforts to revive the deal, but those attempts have been fruitless so far with talks on hold since 2022.