"We've known about the potential for that system to be sold to Iran for several years and have accounted for it in all of our plans," General Martin Dempsey, chairman of the US Joint Chiefs of Staff, told a news conference yesterday.
The United States for years has refused to rule out possible military action to stop Iran from acquiring nuclear weapons if diplomacy fails. Dempsey said the military option would not be undermined by Russia's decision this week to supply Iran with the sophisticated S-300 missiles.
Moscow said progress in nuclear talks between Iran and world powers meant there was no longer a need for Russia to prohibit exporting the surface-to-air missiles to Tehran.
Israel condemned the move by Russia and Washington voiced concern, but Iran hailed the decision as a step towards "lasting security" in the region.
Russia could deliver the missile systems later this year, Ali Shamkhani, secretary of Iran's Supreme National Security Council, was quoted as saying by Russian news agencies.
Although the S-300 would provide a major improvement for Iran's air defense network, it remains unclear if the missile would be a match for America's stealthy F-22 fighters and bombers, experts say.
