“Anyone who attacks us will be very sorry. So if the United States makes such a mistake, they should know that we will definitely respond. And we don’t make threats,” deputy head of Iran’s National Security Council, Brigadier General Mohammed Jafari, tells FRONTLINE in his first television interview.

The West’s relationship with Iran has not been easy. The US and Britain conspired to the overthrow the elected government in 1953, replacing it with the Shah to secure oil rights. When he was ousted by supporters of the Islamic cleric Ayatollah Khomeini in 1979 and radical students captured the US embassy things could only get worse.

Since then, the US has imposed trade sanctions while Iran has been accused of funding and supporting terrorists. Now, fears are growing that Iran is developing nuclear weapons while America’s military supremacy has been dented by the muddled handling of the aftermath of the war in Iraq, while dissent within Iran has led to more sabre rattling by the leadership.

FRONTLINE examines the strained relationship from both sides, tracing the downward spiral since 9/11 from unprecedented early cooperation in Afghanistan to Tehran’s open threats to drive America out of the Middle East.