Iran is the "only power" that can secure the oil-rich Gulf, a Revolutionary Guards commander said on Tuesday, adding that the reinforced US navy presence in the waterway was causing regional instability.

"The only power which can provide for the security in the region is the Islamic Republic of Iran and the world is slowly grasping this issue," said Admiral Ali Fadavi, the Guards' top naval chief, quoted by the website of the Bushehr provincial governor's office (ostb.ir).

Tehran has often denounced the deployment of "foreign forces," especially US ones, in the Gulf.

However, its leaders usually assert that "the region's countries" must jointly ensure security. Fadavi's reported comments were unusual in asserting that Iran, alone, should be the Gulf's guardian.

Fadavi's comments were made ahead of September 16-27 war games the United States and 20 other nations are to hold near the Gulf.

The exercises will test abilities to clear waters of mines -- a tactic the United States fears Iran could use to impede oil tanker traffic in the narrow Strait of Hormuz, at the mouth of the Gulf.

Iran has threatened to block that chokepoint if sanctions prevent it exporting its own oil, or if it is subject to air strikes that Israel has threatened to unleash to damage its nuclear facilities.

Washington has warned Tehran that any attempt to close the strait would be viewed as a "red line" -- grounds for US military action.

Two US aircraft carriers are already in or near the Gulf, with a third on the way, a greater-than-normal show of US naval might in the region.

Some Arab nations in the Gulf host US military bases, notably Bahrain, which is home to the headquarters of the US Fifth Fleet, and Saudi Arabia.

"The presence of the Americans causes insecurity in the Persian Gulf, the Strait of Hormuz and the Sea of Oman," Fadavi said.

"The Americans live with the delusion that they are powerful. But the Islamic Revolution's power is derived from God's eternal power and it is incomparable," he added.

The naval arm of Iran's Revolutionary Guards, with its 20,000 servicemen, is tasked with defending territorial waters in the Gulf, while Iran's regular navy is deployed to the Indian Ocean and beyond.

Arab monarchies on the opposite side of the Gulf from Iran are worried by what they see as hegemonic ambitions by the Islamic republic, which frequently underlines Persia's historic dominance over the waterway.