Iran is on alert and will "punish" any Israeli strike against it, its armed forces chief of staff, General Hassan Firouzabadi, warned on Wednesday amid Israeli media speculation of plans for an attack.
"We consider any threat -- even those with low probability and distant -- as a definite threat. We are on full alert," he said, quoted by Fars news agency.
"With the right equipment, we are ready to punish them amd make them regret (committing) any mistake," he said.
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Firouzabadi also said the United States "will suffer serious damages should there be a military attack by the Zionist regime against Iran."
Media in Israel are speculating that there are plans to attack Iran's nuclear facilities but that the government was split on the issue.
Israeli Defence Minister Ehud Barak on Monday denied that he and Prime Minister Benjamin Netanyahu had already decided to launch an attack against Iran over the opposition of military and intelligence chiefs.
Israel and several Western nations accuse Iran of seeking to build an atomic arsenal under cover of its nuclear energy programme, despite Tehran's repeated denials.
Israel itself is widely held to possess several hundred nuclear missiles but has a policy of neither confirming nor denying that.