Major-General Hassan Firouzabadi's comments came despite an offer by President Barack Obama to engage in direct talks with Tehran if it "unclenches its fist," and may disappoint Washington.
Iran has reacted cautiously to Obama's offer, saying it wants to see real change in U.S. policy after the Republican administration of George W. Bush spearheaded a drive to isolate Tehran over its controversial nuclear program.
Supreme Leader Ayatollah Ali Khamenei, Iran's highest authority, last week said Obama was pursuing the same "wrong path" as Bush in supporting Israel, Iran's arch enemy.
In a swift overture to Iran, Washington on March 5 said it would invite Tehran to an international meeting on Afghanistan. Iran has said it will consider the request.
While reaching out to Iran, the Democratic administration has not ruled out possible military action if diplomacy fails to end the dispute over a nuclear program that the West suspects is aimed at making bombs. Tehran denies the charge.
"We cannot claim that the (U.S.) Democrats are not warmongering like the Republicans. They are just as warmongering and mischievous, and they would like to do that (attack Iran)," Firouzabadi said.
"But they are unable to do that and there is no way to stage an attack against Iran. America is not able to incur the cost of attacking Iran," he was quoted as saying by the ISNA news agency on the sidelines of a conference in Tehran.
Iran has said it would respond to any attack by targeting U.S. interests and Israel, as well as closing the Strait of Hormuz, a waterway between the Gulf and the Sea of Oman through which about 40 percent of the world's traded oil is shipped.
Israel, believed to be the only nuclear-armed state in the Middle East, has said Iran's nuclear plans threaten its existence. Like the United States, it has not ruled out military action.
(Reporting by Hashem Kalantari; Writing by Fredrik Dahl; Editing by Kevin Liffey)
