DUBAI, United Arab Emirates — A new international naval force under American command will soon begin patrols to confront escalating attacks by Somali pirates after more than 100 ships came under siege in the past year, the U.S. Navy said Thursday.

There currently are more than a dozen warships in the vast expanse off the coast of Somalia, from naval giants such as the U.S., Britain and Russia, emerging powers such as China and India and regional forces such as Iran.

The announcement on the new mission — issued by the U.S. 5th Fleet in Bahrain — said more than 20 nations are expected to take part and it will be headed by U.S. Navy Rear Admiral Terence McKnight.