Russian President Dmitry Medvedev issued a decree Wednesday banning all sales of S-300 anti-aircraft missile systems to Iran.
Russia signed a 2007 contract to sell the sophisticated systems that could boost Iran's ability to defend against air strikes. Israel and the United States have objected to the deal, and no such missiles have been delivered yet.
Medvedev's decree also prohibited exports of tanks, aircraft and sea vessels to Iran.
Russia has recently has shown increasing frustration with Iran's policies. It has said United Nations sanctions would prevent it from delivering the S-300s to Iran.
The S-300 is capable of shooting down aircraft and missiles at ranges of over 90 miles and at altitudes of about 90,000 feet.
In Washington, the White House issued a statement welcoming the executive order signed by Medvedev.
"We believe President Medvedev has demonstrated leadership on holding Iran accountable to its international obligations from start to finish," said Mike Hammer, a spokesman for the National Security Council.