Iran has denied allegations made by U.S. Secretary of State Mike Pompeo that it was behind the attacks on Saturday, which were claimed by Yemen's Iran-aligned Houthi group. Sunni Saudi Arabia and Shi'ite-led Iran back opposing factions across the Middle East, from Yemen and Syria to Lebanon and Iraq. Saudi Arabia is leading a military coalition to back Yemen's internationally recognised government against the Houthis.

A senior Iranian official said the heightened tensions over the assaults could tip the balance of power in Iran in favour of hardliners looking to constrain pragmatist President Hassan Rouhani's ability to open up to the West.

Iran's top authority Supreme Leader Ayatollah Ali Khamenei's aversion to the United States remains a formidable barrier to any diplomatic solution, despite the likely benefits for Iran's sanction-hit economy.