Gholam Hossein Nozari also said that military moves against Tehran would cause even greater volatility in oil markets that are seeing new price records set almost daily.

Mr Nozari spoke to reporters today outside the 19th World Petroleum Congress in Madrid, Spain, which is looking for answers on how to stabilise prices and ensure secure supplies of energy for the future.

"Iran, if there were any kind of activity of any sort, is not going to be quiet and would react fiercely," he told said.

"When just a statement (about a possible attack) makes this much volatility in the market, can you imagine that if any action happens ... what would be the result in the oil market?

"Iran has always been a reliable source of supply to the market and Iran remains a supplier forever."

Meanwhile, an adviser to Iran's supreme leader Ayatollah Ali Khamenei said a compromise is possible in the country's stand-off with the West over its nuclear programme.

Ali Akbar Velayati wrote a commentary for France's Liberation newspaper saying that Iran's nuclear power technology must be preserved for the future.

The former foreign minister also says Iran's adherence to the Nuclear Non-Proliferation Treaty gives it rights in exchange for its commitments.

Mr Velayati writes: "That's how a compromise could be reached on the common concerns of Iran and other states."

His comments appeared today in Liberation. The United States and some allies fear Iran wants to produce nuclear weapons - a claim Iran denies.