The United States and 25 allies were in the midst of a massive 12-day navy drill Tuesday in strategic Middle East waterways. This year’s war games are believed to be the largest ever undertaken in the region.

The annual drill comes amid amid threats of war between Israel and Iran over the Islamic regime’s nuclear program.

The exercises, IMCMEX-12, focused on clearing mines that Tehran, or guerrilla groups, may deploy to disrupt oil tanker traffic in the Strait of Hormuz. The drill, according to participants, underlines their determination to keep oil shipping lanes open in case of regional turmoil.

“Planning was completed last week for the exercise that will focus on a hypothetical threat to mine the international strategic waterways of the Middle East, including the Red Sea, the Gulf of Aden, the Gulf of Oman, and the Persian Gulf,” the US Central Command said in a statement, Bloomberg reported.

The United States, Britain, France, Saudi Arabia and the UAE were among the chief participants. Cruisers, aircraft carriers, minesweepers, and other vessels were taking part.

Some 18 million barrels of oil flow through the Strait of Hormuz each day — about 35 percent of the world’s oil that is traded by sea. One of the world’s most congested waterways, it is 21 miles wide at its most narrow point and it is bordered by the Iranian coast, on the north, and the Arabian peninsula, to the south.

The shipping strait has a contentious past — Iran regularly claims the waterway is part of its territory. US Defense Secretary Leon Panetta has stated that Iranian aggression in the waterway would be met with force from the US.