In a nosedive for French-Iranian relations, Paris is telling its diplomats and foreign ministry officials to postpone indefinitely any non-essential trips to the Islamic Republic.

An internal memo obtained by Reuters has French officials citing a foiled plot to bomb a rally held by an exiled Iranian opposition group members near Paris earlier in the summer that was attended as well by Rudy Giuliani, Trump's lawyer and former New York mayor.

The French government has not publicly implicated Iran in the plot, but it also cited a hardening of Tehran's attitude to France.

The warning comes as Iran is trying to shore up support among European allies for its tattered nuclear deal.

The US pulled out in May and re-imposed sanctions.

France has been one of the strongest advocates of saving the 2015 pact between Iran and world powers.

The French foreign ministry declined to comment on the memo or say whether embassy staff had been asked to repatriate their families.

Iranian officials at the embassy in Paris did not respond to a request for comment.

The memo underscores how confidence in the Tehran government has been eroded, even as President Emmanuel Macron talks up preserving the nuclear accord