Reporting from Tehran and Beirut — Iran has left little doubt that it wants to buy a sophisticated antiaircraft weapons system from Russia. The confusion in recent days has been over the question: Has Moscow said yes? Under pressure from Israel, which views Iran as one of its major threats in the Middle East, Russian officials have promised not to sell S-300 mobile long-range defensive weapons to Tehran. But a flurry of recent conflicting reports has muddled the matter. On Monday, Iran’s Foreign Ministry spokesman was cagey. Hassan Qashqavi told reporters that he had not “received any report” regarding the missiles from “relevant” officials.