What weapons could be used in strikes against Syria?
As the United States considers military action against Syria in response to a disputed chemical weapons attack on civilians, we profile some of the weapons that may be deployed by both sides in the days ahead.
Tomahawk cruise missile
These missiles can be launched from ship or submarine. They are equipped with small turbofan engines, similar to commercial airliners, which they use to cruise to their targets.
They have a small cross-section, fly at low altitudes and are very difficult to detect. Tomahawks emit little heat so they cannot be picked up by infrared detection.
They have a range of about 1,000 miles (1,600km) and fly at a speed of about 550mph (880 km/h).
The missile reaches its target by using Terrain Contour Matching software, which works by matching the view on the ground with a map of its route. It carries a warhead of between 1,000lb and 3,000lb (450kg-1,360kg).
Arleigh Burke-class destroyer
The US has four Arleigh Burke-class destroyers in the eastern Mediterranean.
The ship is 505ft (154m) long and can carry cruise missiles. It is one of the largest and most heavily armed of the US destroyers.
It was the first US warship designed with an air-filtration system to protect against nuclear, biological and chemical warfare.
The United States has two aircraft carriers in the region, the USS Harry S Truman and the USS Nimitz. Both of these huge nuclear-powered warships are more than capable of launching air strikes, but if limited action is planned by the Americans then they may not come into use.
The carriers are some of the largest in the world, at nearly 1,100ft (330m) long and have a complement of up to 85 aircraft.
The F-16 has a reputation as one of the most reliable, manoeuvrable and effective military aircraft in the world.
It is a multi-role fighter, with the ability to attack other planes in the air and seek out and destroy targets on the ground.
The planes are the backbone of the US Air Force and when first introduced they brought the innovation of fly-by-wire, rather than mechanical cable, controls to fighter planes.
It has a range of about 2,000 miles (3,220km), which allows it to remain in combat zones longer than other aircraft. It is armed with an M61 vulcan cannon and the pilot sits in a frameless bubble canopy for better visibility.
F-16s based at Incirlik or Izmir in Turkey, or possibly also operating from Jordan, could be used in any possible strikes against Syria.
F-15 Strike Eagle
Another multi-role aircraft, the F-15 was designed for long-range, high-speed ground attacks.
The combined thrust from its two engines means it can accelerate even when going straight upwards.
F15E Strike Eagles are equipped with the "Lantirn" navigation and targeting system, which aims to improve the accuracy of attacks by using infrared or laser-guided bombs.
It has terrain-following radar, which can be linked to the plane's autopilot so it can follow the contours of the landscape at a height of just 100ft (30m).
Anti-chemical weapon munitions
The Pentagon has been developing specific munitions for attacking chemical weapons stores and production facilities. For example a bomb designated "crash pad" is designed to incinerate the target at sufficiently high temperatures to destroy all the chemicals involved.
Given the scale of Syria's chemical weapons infrastructure and the proximity of much of it to heavily populated areas, it is a moot point whether such munitions might be employed in any US strike against Syria.
Should France take part in any strikes, it has Scalp cruise missiles with a range of about 300 miles (500km) which can be fired from Mirage 2000 and Rafale warplanes.
It also has an aircraft carrier in the Mediterranean and air bases in the United Arab Emirates.
The Charles de Gaulle, currently at Toulon, is a nuclear-powered carrier capable of carrying up to 40 combat aircraft. It has a ship's company of just under 2,000 personnel. Although smaller than the US Nimitz Class carriers it is still an impressive ship coming in at 860ft (262m) long.
Russia has said it is sending two warships to the Mediterranean, a missile cruiser, the Moskva, and an anti-submarine ship. Russia is an ally of Syria and opposes military intervention.
Exactly when the two vessels will arrive in the region is unclear, but their deployment has been described by Russia as part of a planned rotation of its ships in the Mediterranean.
Key Syrian weapons
S-200 Angara anti-aircraft missile
The S-200 missile, known to Nato by the codename SA-5 "Gammon", is a venerable anti-aircraft missile designed by Russia in the 1960s.
Analysis by the Center for Strategic and International Studies suggests that Syria probably has eight S-200 batteries deployed between two air defence regiments.
The missile is liquid fuelled and designed to fly at speeds of up to Mach 8. It is guided to its target by radar, before detonating a 217kg (478lb) high-explosive warhead.
Russia began to phase the S-200 out more than 20 years ago and the system is considered obsolete by military analysts. There are also doubts about the integrity of the system due to the loss of some airbases and radar sites to rebel groups.
S-300 anti-aircraft missile system - Unconfirmed
The modern and much more capable S-300 has been ordered by Syria from Russia, but there are doubts as to whether the system has actually been delivered, of if it has, whether it is operational.
The S-300 is a long-range, surface-to-air missile designed to protect military and industrial facilities against enemy aircraft and cruise missiles.
With an integrated radar system which can track 100 targets at a time, it is considered one of the most potent air defence weapons in the world.
P-800 Yakhont anti-shipping missile
The P-800 Yakhont, known to Nato as the SS-N-26, is a sophisticated anti-shipping missile of Russian origin.
The supersonic missiles have a range of 300km (200 miles), carry a 200kg (440lb) warhead, and are able to fly at an altitude of only 5-15m (16-50ft), making it difficult to detect and intercept them.
The Syrian Air Force has a variety of combat aircraft acquired mostly from Russia, but many are old and obsolete.
A report by the Institute for the Study of War (ISW) in May 2013 also suggested that the most effective "MiG and SU aircraft require significant spare parts supply, maintenance, and training to remain mission capable".
Given these operational difficulties, the ISW found that since the start of the conflict, the air force had instead mostly used the more robust, but less capable L-39 trainer aircraft in a ground-attack role against rebel forces.