A major US-led naval minesweeping exercise got underway in the Gulf Sunday as tension remain high over Iran and its controversial nuclear program.

The exercise kicked off on the same day the head of Iran's Revolutionary Guards warned of retaliation against the Strait of Hormuz, Israel and nearby US bases if his country is attacked, and as Israeli Prime Minister Benjamin Netanyahu insisted on a "red line" from Washington, claiming Tehran is "90 percent" toward having a nuclear bomb.

The September 16-27 International Mine Countermeasures Exercise (IMCMEX) includes military forces from more than 20 nations, the US naval forces Central Command in Manama, Bahrain said in a statement.

The navy ships will "participate in the defensive exercise to preserve freedom of navigation in the international waterways of the Middle East and promote regional stability" in the region, the statement read.

The ships "will respond to simulated sea-mine attacks in international waters and clear maritime routes to restore freedom of navigation."

US defense officials insist the exercise is not aimed at Iran or any one country, but is simply designed to hone counter-mine capabilities among allies and partners.

"This exercise is about mines and the international effort to clear them," said US Vice Admiral John Miller, the head of the US Naval Forces in the wider Gulf region.

The statement emphasized that the event is a "wholly defensive exercise."

Iranian General Mohammad Ali Jafari, speaking in a rare news conference in Tehran on Sunday, said the Strait of Hormuz -- the narrow channel at the entrance of the Gulf through which a third of the world's traded oil passes -- would be a legitimate target for Iran should it be attacked.

Jafari also suggested that US military bases -- such as those in Bahrain, Kuwait, the United Arab Emirates and Saudi Arabia -- would be fair game for retaliation by Iran or proxy forces.

And if Israeli jets or missiles struck Iran, "nothing of Israel will be left, considering its size," he warned.

The Israeli leader, speaking on two US political television talkshows, pressed the need for a categorical bar on Iran, saying such a safeguard had averted nuclear calamity with Russia during the Cold War and could ensure peace again.

Washington says all options against Iran, including military action, remain on the table, but top officials reject so-called "red lines" as political grandstanding that might leave them at a strategic disadvantage.