USS Mahan
The Arleigh Burke-class destroyer DDG-72 is armed with Tomahawk cruise missiles capable of striking Syrian targets. The Navy ship was active in Operation Unified Protector, the 2011 NATO campaign against Libyan leader Muammar Gaddafi. Officials said the ship would soon be relieved by USS Stout but would remain in place for the time being.
USS Stout
On Thursday, Stout was heading east to relieve the USS Mahan, according to Pentagon officials. But US officials had originally said this destroyer would not take part in any strikes, as it entered the Mediterranean through the Straits of Gibraltar on Tuesday.
USS Gravely
The Arleigh Burke-class destroyer DDG-107 is armed with Tomahawk cruise missiles capable of striking Syrian targets. The ship was commissioned in late 2010 and is part of Carrier Strike Group Two.
USS Barry
Arleigh Burke-class destroyer DDG-52 is armed with Tomahawk cruise missiles capable of striking Syrian targets. In 2011, the ship launched some 55 such missiles against Libyan air defences as part of Operation Odyssey Dawn.
Incirlik Air Base
As part of the 39th Air Base Wing, the 5,000 US airmen who reside here could be drawn into a campaign against Syria.
Akrotiri Air Base
This potential staging ground for an allied effort against Syrian targets reportedly saw an upsurge in activity starting on Monday, with military transport plans and fighter jets arriving from continental Europe. The base is less than 100 kilometers from Syria and hosts British airmen.
KASOTC
After a military exercise in June, the US kept F16 fighters and Patriot air defence missiles at the King Abdullah II Special Operations Training Center in Jordan to prevent spillover from the Syrian conflict.
Udeid Air Base
Large US airfield in Qatar could send B-1 stealth bombers to Syria capable of striking beyond the range of air defense systems. These planes are able to drop munitions on a much wider area than cruise missiles fired from the sea can destroy.
US submarine
A nuclear-powered attack submarine is reportedly readying for combat somewhere in the Mediterranean Sea. These vessels can launch Tomahawk missiles from a range of 1,600 kilometers.
USS Nimitz
Pacific aircraft carrier from Everett, Washington, is conducting maritime security operations with the 5th Fleet. Carrier Air Wing Eleven is attached to Nimitz, which is associated with Operation Enduring Freedom in Afghanistan. The nine accompanying naval fighter jet squadrons include F/A-18C Hornet, E-2C Hawkeye, and MH-60S Knighthawk planes. The group is from Naval Air Station Lemoore, California, and is known by the nickname "Barbwire".
USS Harry Truman
Atlantic aircraft carrier from Norfolk, Virginia, conducting maritime security operations in the Gulf of Aden with the 5th Fleet. The accompanying Carrier Air Wing Three is known as "Battle Axe" and has seen action in World War II, Korea, Cuba, Libya, and other areas. The group's eight squadrons include Electronic Attack Squadron 130 (Zappers) and Strike Fighter Squadron 37 (Raging Bulls).
USS Kearsarge
A large-deck amphibious ship that is part of a readiness group with the San Antonio, is also on the way toward Red Sea after a port call in the United Arab Emirates. The Kearsarge, which carries 6 AV-8B Harriers, 10-12 V-22 Ospreys and helicopters, played a key role in the 2011 strikes on Libya. Two Ospreys launched from the ship helped rescue a downed F-15 pilot during that operation.
USS San Antonio
The amphibious ship is carrying 300 marines and extensive communications equipment. The ship could serve as a floating forward staging base, providing a temporary base for special operation forces, if needed.