Differences over the scope for the talks have also cast doubts on whether it will still go ahead, keeping open the risk of U.S. military action.

US President Donald Trump warned that Iran’s supreme leader should be “very worried,” as both sides prepare for their first formal negotiations since the United States bombed Tehran’s nuclear program last year.

The U.S. Virtual Embassy Iran has repeated a warning to Americans to leave the country now in new advice

Ayatollah Ali Khamenei, Iran’s supreme leader, has vowed to unleash a regional war if America launches air strikes. Initially few in the Middle East seemed eager for further conflict. The region’s power-brokers tried to dissuade America from military action. But attitudes now look more mixed.

As EU designates Iran's IRGC as terrorist group, pressure mounts on U.K. to act as London center allegedly promoting Iranian regime propaganda.

The authorities are making mass arrests, seizing assets and hunting down doctors who treated protesters. Some Iranians keep showing defiance anyway.

"Riyadh is firmly opposed to any US or Israeli military action against Iran at this stage," a former Saudi adviser told Newsweek.

The heavy-handed response to protests has deepened people’s hatred of the regime, and Iranians are speaking out.