The operation, known as IMCMEX-12, focuses on clearing mines that Tehran, or guerrilla groups, might deploy to disrupt tanker traffic, notably in the Strait of Hormuz, between Iran and the Arabian Peninsula.

The start of the event, with a symposium for officers from more than 30 navies, came as Israeli Prime Minister Benjamin Netanyahu told US television viewers on Sunday that Tehran was close to being able to build a nuclear bomb; his words fuelled talk of an Israeli strike, and of Netanyahu pressuring President Barack Obama to back Israel as Obama battles for re-election.

Military officials, diplomats and analysts, as well as Iran itself, all sought to play down the significance of the timing and to stress the defensive and hypothetical aspects of the exercise, which moves on to the water from Thursday with ships from a much smaller number of nations taking part in the maneuvers.

However, it was a clearly deliberate demonstration of the determination on the part of a broad coalition of states to counter any attempt Iran might make to disrupt Gulf shipping in retaliation for an Israeli or US strike on its nuclear facilities, a form of retaliation Iran has repeatedly threatened.

"This exercise is about mines and the international effort to clear them," Vice Admiral John Miller, commander of the US Naval Forces Central Command, told officers assembled for the symposium at his fleet headquarters in Bahrain on Monday. "Represented here are the best of our individual countries' efforts dedicated to securing the global maritime commons."

Reuters