US President Donald Trump's senior envoy Steve Witkoff (Photo:REUTERS/Ammar Awad)

They said Witkoff's visit is expected to begin Tuesday and will discuss Iran crisis. The envoy’s return to the Middle East follows reports that Washington and Tehran are preparing for talks to ease tensions. Witkoff is expected to meet with Iranian officials this week, with Ankara, Turkey, seen as a possible venue.

Iran's semi-official Tasnim news agency confirmed that senior officials from the US and Iran will probably begin negotiations in the coming days, led on the Iranian side by Foreign Minister Abbas Araghchi.

Iranian Foreign Ministry spokesman Esmaeil Baghaei said Iran is reviewing the details and general outlines of the potential negotiations with the US, adding that regional countries are acting as intermediaries exchanging messages between the two sides.

Iran said Monday it has summoned all of the European Union ambassadors in Tehran to protest the EU's decision to classify the Islamic Revolutionary Guard Corps (IRGC) as a terrorist group.