MOSCOW—Russia is moving ahead with a deal to deliver advanced surface-to-air missiles to Iran, the head of the country’s state-run industrial holding company said Monday, according to Russian news agencies. “The contract for the delivery of the S-300 to Iran was not only signed, but has already entered into force,” said Sergei Chemezov, the head of Rostec Corp., the conglomerate that includes arms exporter Rosobornexport, according to state news agency RIA Novosti. Less clear, however, is when the missile system might actually be delivered. The Kremlin lifted a self-imposed ban on the delivery of the weapons system this spring, prompting sharp criticism from the U.S. and Israel. The U.S. and its allies worry the air-defense system would blunt their military edge in the Middle East by giving Tehran a more effective weapon to counter aircraft and cruise missiles. Russia concluded a contract with Iran in 2007 worth roughly $800 […]