The US says the exercises are not aimed at Iran, who earlier vowed to close the Hormuz Strait, and now expresses concern over the drills.

The US Navy has issued a statement that the mass exercises are aimed at “enhancing capability to preserve freedom of navigation in international waterways.” The drills will reportedly focus on mine-sweeping and search-and-seizure operations, and some on-shore training.

The Pentagon is directing the maneuvers, which will reportedly involve 35 ships, 18 unmanned submarines and unmanned aircraft. The 40 other countries participating in the drills have not yet been named; Britain, France, some Middle Eastern states, and nations as distant as New Zealand have previously participated in similar exercises.

The Obama administration has stated that the maneuvers are not a warning to Iran, and are intended solely to secure a key oil route in the region.