"We are ready for the decisive battle with America and the Zionist regime (Israel)," Fars news agency quoted Firouzabadi as saying.
He also warned neighbouring nations not to allow any attack to be launched on Iran from their soil.
"We do not have any hostility towards regional states, but if we are ever attacked from the American bases in the region we will strike that area back," he said.
Washington has many military bases in the region, including in Bahrain, Kuwait, the United Arab Emirates, Saudi Arabia and Turkey.
But Firouzabadi accused the US of bluffing.
"Over the past decade, they brought their forces but came to the conclusion that they can't attack us and left," he said, dismissing the US military threat as nothing but a "political bluff".
President Hassan Rouhani said yesterday the West should not have and delusions about using a military option.
"I say explicitly, if some have delusions of having any threats against Iran on their tables, they need to wear new glasses. There is no military option against Iran on any table in the world," he said.
Western nations have long suspected Iran of covertly pursuing nuclear weapons alongside its civilian programme, allegations denied by Tehran which insists its nuclear activities are entirely peaceful.
Neither the United States nor Israel has ruled out military action to prevent Iran from developing a nuclear weapon, if diplomacy fails.