A U.S. official said Friday that 2,500 more Marines with the 31st Marine Expeditionary Unit and the amphibious assault ship USS Tripoli were being sent to the Middle East, adding to the military’s largest buildup of warships and aircraft in the region in decades.

The official spoke on condition of anonymity to discuss sensitive military plans.

Marine Expeditionary Units can conduct amphibious landings but also specialize in bolstering security at embassies, evacuating civilians, and providing disaster relief. The deployment doesn’t necessarily indicate that a ground operation will take place. The Wall Street Journal first reported the Marine deployment.

The Tripoli was spotted by commercial satellites sailing near Taiwan, putting it more than a week away from waters off Iran.

Earlier in the week, the Navy had 12 ships, including the aircraft carrier USS Abraham Lincoln and eight destroyers, in the Arabian Sea. The total number of U.S. service members on the ground in the Middle East is not clear.

(AP)