The United States called Tuesday for international action to hold Iran to account after Saudi Arabia accused Tehran of “direct military aggression” over a Yemeni rebel missile attack near Riyadh. The Iran-backed Huthi rebels also threatened to attack ports and airports in Saudi Arabia and the United Arab Emirates, escalating a crisis between Riyadh and Tehran. Saudi Arabia’s powerful crown prince had accused Iran of supplying missiles to the Huthis, which he said “could be considered as an act of war”.