WASHINGTON – The United States and 29 other nations have begun the biggest mine-clearing exercise in the Persian Gulf region, a show of force as tensions escalate over a threatened Israeli attack on Iran’s nuclear facilities.

The 12-day exercise that started Sunday involves Western nations such as Britain and France, as well as participants as varied as Japan, Yemen, Jordan, New Zealand and Estonia, according to the U.S. Navy.

In an effort to avoid a showdown with the Islamic Republic, it won’t extend into the Strait of Hormuz, the waterway between Iran and Oman through which as much as a fifth of the world’s traded oil is shipped daily.

In addition to serving as a warning to Iran, the display of power will “signal to Israel that the United States has a military option available” and show “U.S. resolve to its Persian Gulf allies, especially in the face of repeated Iranian threats to try to close the Strait of Hormuz,” said Kenneth Katzman, a Middle East specialist for the nonpartisan Congressional Research Service in Washington.

Participating nations will conduct mine-hunting and mine-countermeasure operations with MH-53E Sea Dragon helicopters, as well as explosive ordnance disposal, diving, and small-boat exercises and port-clearance operations focused on underwater improvised explosive devices, according to the U.S. Navy 5th Fleet, which is headquartered in Bahrain.

Iranian officials have periodically threatened to close the Strait, which is 21 miles wide at its narrowest point, in retaliation for tightening international sanctions aimed at dissuading them from developing a nuclear weapon. Laying mines or sinking a ship in the Strait would disrupt tanker traffic and also prompt insurance companies to raise rates on tankers, leading at least temporarily to higher oil prices.