to provide under a 2007 contract to sell the S-300s.</p>

<p>The sophisticated S-300 anti-aircraft missiles would significantly boost Iran's ability to defend against airstrikes. Israel and the United States have strongly objected to the deal.</p>

<p>Russia has walked a fine line on Iran for years. One of six world powers leading international efforts to ensure Iran does not develop a nuclear weapon, it has strongly criticized the U.S. and the European Union for following up with separate sanctions after t