Yury Baluyevsky, the head of the armed forces' General Staff, said: "Inflicting damage on Iran's military and industrial potential might be realistic, but winning [the war] is unachievable - its reverberations would be heard across the world."
Baluyevsky said that when making a decision on Iran, U.S. leaders should bear in mind the negative experience in other countries of the region.
"Our strategic partners have already got bogged down in Afghanistan and Iraq," he said.
He warned that if the U.S. goes to war with Iran as well, the world may see America decline as the world's "mightiest and most powerful state."
The U.S. Administration sees Iran as a "rogue state" belonging to what President George W. Bush has termed "an axis of evil," and is determined to stop the Islamic Republic - diplomatically or otherwise - from obtaining a nuclear weapon. It now plans to deploy a national missile defense shield in Central Europe, which it says will help protect its own security and that of its European allies against potential missile strikes from Iran, suspected by the West of pursuing a covert nuclear weapons program.