would take action if the United States were to carry out an act of "stupidity" and attack Syria,
an Iranian military official was quoted as saying on Saturday, but the comments later disappeared from the state-linked agency website.
Iran has steadfastly supported Syrian President Bashar Assad
in his bid to suppress an uprising which both Tehran and Damascus
see as a proxy war by Israel
and Western states to extend their influence in the Middle East.
"If America were to attack Syria, Iran along with Syria's allies will take action, which would amount to a fiasco for America," Mohammad Ali Assoudi, the deputy for culture and propaganda of the Islamic Revolutionary Guard Corps (IRGC), was quoted as saying.
Assoudi's comments were first carried by the government-linked news agency Young Journalists' Club but were later apparently taken down from the group's website. The comments were picked up by Iranian news sites including Iran's Jam-e Jam newspaper and the BBC's Persian-language site.
Iranian officials were not immediately available for comment.
Assoudi did not specify exactly what steps Iran would take, but said Syria's allies would implement their joint military pact in the case of a US attack.
"In the case of American stupidity and a military attack by this country on Syria, the joint military pact of Syria's allies would be implemented," Assoudi said.
Iran and Syria signed a mutual defense pact in 2006, but little is known of its details, or whether there are any other signatories.
The Islamic Republic considers Assad's government, along with Lebanese Shiite terrorist group Hezbollah,
part of an "axis of resistance" against the influence of the United States and Israel in the Middle East.
But while Turkey, Gulf Arab countries and Western states admit to giving non-weapons aid to the Syrian rebels, there is little or no appetite in Washington,
especially in an election year, for direct military intervention in Syria. Without US leadership, its allies also appear unwilling to go it alone.
Iran accuses Western powers and regional states of supporting and arming the rebels, while the rebels accuse Iran of sending IRGC fighters to help Assad crush the uprising.
"With cooperation from Qatar, Turkey
and Saudi Arabia,
America has the goal of striking a blow against Syria and making preparations for the fall of the Syrian government," Assoudi said.