Yahya Rahim Safavi, commander in chief of the Revolutionary Guard, told state television on Saturday: "If we come under a military attack, we will respond with our very effective missile defence."
Western states suspect Iran of secretly aiming to build a nuclear bomb. Tehran insists its nuclear facilities are intended to produce only electricity.
The United States and Israel have said they will prefer to solve the stand-off through diplomacy but have not ruled out a military strike.
Military experts reckon the Revolutionary Guard's Shahab-3 missiles have a range of 2000km, meaning Israel, US bases in the Gulf and foreign troops in Iraq lie within their range.
Safavi repeated Tehran's allegations that Britain and the US are arming rebels in the southwestern province of Khuzestan, which has most of Iran's abundant oil reserves.
"Occupying forces in Iraq, particularly those in the south, provide Iranian agents with material for bombing," he said.
"British and US intelligence services should avoid interfering in our affairs."
Bombs ripped through a bank and government building in Khuzestan city of Ahvaz on Tuesday, killing eight people.
But Manouchehr Mottaki, the Iranian foreign minister, said Tehran was willing to work with Britain to put an end to the violence.
"Iran's security officials have said they are ready to hand over to British oficials the documents related to the previous and recent incidents in Ahvaz," Mottaki told a news conference.
"British and US intelligence services should avoid interfering in our affairs"
Yahya Rahim Safavi,
Commander-in-Chief of Iran's
"That would be done soon and we hope that, by means of constant follow-ups, we reach tangible results that could prevent such events from happening again."
A group fighting for the independence of Iran's Arab minority claimed responsibility for Tuesday's attacks but the claim could not be verified.