Iran's supreme leader denounced on Wednesday US "nuclear threats" against the Islamic Republic, and its elite military force said it would stage war games in a waterway crucial for global oil supplies.
The Revolutionary Guards' exercises in the Gulf and the Strait of Hormuz this week take place at a time of rising tension between Iran and the West, which fears Tehran's nuclear program is aimed at developing bombs. Iran denies the charge.
Iran has also reacted angrily to what is sees as US President Barack Obama's threat to attack it with nuclear arms.
Obama made clear this month that Iran and North Korea were excluded from new limits on the use of US atomic weapons - something Tehran interpreted as a threat from a long-standing adversary.
"The international community should not let Obama get away with nuclear threats," Supreme Leader Ayatollah Ali Khamenei said on Wednesday.
"We will not allow America to renew its hellish dominance over Iran by using such threats," he told a gathering of Iranian nurses, the semi-official Fars News Agency reported. Iran was a close U.S. ally before its 1979 Islamic revolution.
Brigadier General Hossein Salami, also quoted by Fars, said three days of maneuvers would start on Thursday and would show the Guards' naval strength.
"Maintaining security in the Persian Gulf and the Strait of Hormuz, as the world's key economic and energy routes, is the main goal of the war games," he said. "This war game is not a threat for any friendly countries."
Naval, air and ground forces from the Guards would take part, Fars said. The Islamic Republic's armed forces often hold drills in an apparent bid to show their readiness to deter any military action by Israel or the United States, its arch foes.
'Peace and friendship'
Nicole Stracke, a researcher at the Gulf Research Center in Dubai, said that with the "current threat to Iran increasing" the Guards were showing their capability and strength.
"The Revolutionary Guard is sending a message that we are ready and able to counter the threat," Stracke said in an e-mail to Reuters. But she added the force regularly held such drills and they were unlikely to increase regional tension.
Washington is pushing for a fourth round of UN sanctions on Tehran over its refusal to halt sensitive nuclear activities as demanded by the UN Security Council, including moves against members of the Guards.
Israel, widely believed to have the Middle East's only atomic arsenal, has described Iran's nuclear program as a threat to its existence. Although it says it wants a diplomatic solution, Washington has also not ruled out military action.
Iran, a predominantly Shiite Muslim state, has said it would respond to any attack by targeting US interests in the region and Israel, as well as closing the Strait of Hormuz. About 40% of the world's traded oil leaves the Gulf region through the strategic narrows.
Salami made no reference to this in his comments, stressing Iran's "efficient and constructive role" for Gulf security.
"Peace and friendship, security, tranquility and mutual trust are the messages of this war game for neighboring countries in the Persian Gulf region," the general added.
Sunni-led Arab countries in the Gulf are concerned about spreading Iranian influence in the region and also share Western fears about Tehran's nuclear ambitions.
Cliff Kupchan, a director of Euroasia Group, said in a note on Wednesday that he still believed that Israel was unlikely to strike Iran, but "the risk will grow as prospects for successful sanctions diminish."
China and Russia, veto-wielding Security Council members, are reluctant to back tough sanctions on Iran.