"All the countries should know that if Iran's interests in the region are ignored, it is natural that we will not allow others to use it (the strait)," said army chief General Hassan Firouzabadi, quoted by the Fars news agency.

However, Iran's armed forces joint chief of staff stressed his country's priority was that the Strait of Hormuz remain open.

Speculation has been rife that Israel could be planning a military strike against Iranian nuclear sites, using force to halt Tehran's controversial atomic activities.

The chief of Iran's elite Revolutionary Guards militia, General Mohammad Ali Jafari, meanwhile, warned that his forces would use "blitzkrieg tactics" in the Gulf if his country came under attack.

"The Guards are equipped with the most advanced missiles that can strike the enemies' vessels and naval equipment with fatal blows," Fars quoted the Guards chief as saying.

In case of attack, "blitzkrieg tactics and operations of the Guards' boats will not leave a chance for the enemies to run away."

"These words do not mean that the prerequisites of war are being set but these are the strategies that our alert armed forces have prepared for any hypothesis," he added.

The new commander of the US Fifth Fleet, Vice Admiral William Gortney, said on Saturday that the American naval presence in the region was "a very clear message that we are here to maintain security and to provide stability."

"The chief of naval operations wanted me here, I think, because of my experience," Gortney, who was navy chief during the US-led invasion of Iraq in 2003, told reporters in Bahrain where the fleet is based.

His predecessor, Vice Admiral Kevin J. Cosgriff, has warned that Fifth Fleet would not allow Iran to close the Strait of Hormuz.

The strait between Iran and Oman is a vital conduit for energy supplies, with as much as 40 percent of the world's crude passing through the strategic waterway.

US President George W. Bush has not ruled out using force in the nuclear standoff between Iran and the West, but emphasised that he preferred a diplomatic solution.

Iran insists its atomic drive is peaceful, but Western powers fear Tehran is using the programme to develop nuclear weapons.

© 2008 Agence France-Presse