European nations are seeking to ensure at least one Iranian bank stays connected to the world after the US imposed new sanctions against the country, a French senator said in Tehran on Sunday.

The United States pulled out of a landmark 2015 nuclear deal with Iran in May and has been reimposing punishing sanctions on the Islamic republic, targeting in particular its financial system.

The European efforts to help Iranians benefit from the nuclear deal despite the US sanctions is "difficult but it"s possible", said French Senator Philippe Bonnecarrere.

One way was "to have at least one Iranian bank remain connected to the international banking system through SWIFT to keep up commercial relations on goods or services that are not subject to sanctions," he added.

Bonnecarrere, who heads the France-Iran friendship group in the upper house of parliament, made the remarks during a news conference with French and Iranian counterparts.

The 2015 nuclear deal was agreed between Iran and the so-called 5+1 group __ UN Security Council permanent members Britain, China, France, Russia and the United States, plus Germany.

Bonnecarrere was in Iran with six other members of the French parliament.