March 19 (Reuters) - Military action authorised by the United Nations against Libyan forces loyal to Muammar Gaddafi could take place under NATO command or under a coalition of the willing led by France and Britain.
NATO said its ambassadors would meet to discuss their response, while analysts expect an initial strike would target Libya's military aircraft, air force bases and communication systems.
Following are assets that could be used in action against Libya, and those belonging to Gaddafi's military:
France, which was at the forefront of the push to take action in Libya, would likely deploy Mirage and Rafale fighters from air bases near the Mediterranean towns of Marseille and Istres or from the island of Corsica.
Airborne refuelling tanker aircraft are also ready to depart from Istres.
Fighter jets could reach Libya in around an hour and a half from the south of France and in around an hour from Corsica.
France's Charles de Gaulle aircraft carrier is at the Mediterranean port of Toulon and could be deployed on Sunday.
The carrier could reach the Libyan coast in one and a half days carrying 15 fighter jets. Its battle group includes three frigates, a fuel-supply ship and an attack submarine.
France rejoined NATO's military command in 2009.
Britain said it would deploy Typhoon patrol jets and all-weather Tornado attack aircraft which are based at Royal Air Force bases in Scotland and the eastern county of Norfolk but would be moved in the coming hours to unidentified bases nearer Libya.
Prime Minister David Cameron told parliament that air-to-air refuelling and surveillance aircraft would also be used.
Britain has two frigates off the Libyan coast: HMS Cumberland and HMS Westminster. The Ministry of Defence said it was not clear if they would be used in any operation and added destroyers could also be deployed.
The Pentagon said that it was ready to carry out orders on Libya but said it would not discuss possible operations.
The U.S. Navy has five combat ships in the Mediterranean, including at least one guided missile destroyer. The United States does not have any aircraft carriers close to Libya.
The USS Enterprise, which in recent weeks was stationed in the Red Sea, has been moved eastwards, away from Libya, to join the USS Carl Vinson, in the Arabian Sea to support Afghanistan operations.
Aviano, south of the Alps in Italy, is the region's only U.S. air base with aircraft assigned to it -- 42 F-16s. The Pentagon has declined to discuss the positioning of other planes in the region.
The United States has a range of military bases and installations in the Mediterranean elsewhere in Italy, Greece, Spain and Turkey.
Italy has given its full support to military action against Libya, saying that it would actively participate and offering its airbases.
Defence Minister Ignazio La Russa said seven bases in Italy -- at Amendola, Gioia del Colle, Sigonella, Aviano, Trapani, Decimomannu and Pantelleria -- were available and some allies had already asked to use them.
Five of them are on the southern mainland or Sicily, making them some of the closest available bases to Libya.
Spain has offered up to six F-18 bombers and an F-100 frigate, as well as troops. Two Spanish bases - Rota in Cadiz and Moron de la Frontera in Sevilla -- are also available for use in the military operation.
Norway said it will make its F-16 fighter jets available for an operation in Libya and could also provide Hercules transport aircraft to assist in humanitarian efforts.
Denmark said it would send six F-16 planes and one military transport plane to support an intervention in Libya. The planes were ready to leave Denmark on Saturday for a southern European base with around 100 personnel including pilots and support.
The Dutch government said it backs the no-fly zone over Libya and would support a military intervention if asked, but has not been asked to contribute for now.
Non-NATO member Sweden is seen as possibly coming into support enforcement of the no-fly zone at a later stage.
Saudi Arabia, the United Arab Emirates and Qatar are seen as the most likely Arab nations to provide back-up for an operation.
Libya's military before the insurrection was on paper made up of 100,000 troops, backed by heavy artillery, tanks, warplanes and a small navy.
Since the rebellion, some members of the armed forces have defected and some hardware has fallen into rebel hands.
The level of rebel strength is difficult to ascertain, but the best-equipped and -trained units -- up to 12,000 men -- have remained loyal to Gaddafi because they are outside the regular army structure and are commanded by family members or people in his inner circle.
Libya's military has been undermined by sanctions and neglect. Much equipment is poorly maintained or unusable.
In Libya's east around Benghazi, regular military forces appear to have either defected to the opposition or melted away. Citizen groups have taken up arms. But analysts say the opposition lacks command and control.
STRENGTH ON PAPER:
GROUND FORCES - Numbers: 50,000 including 25,000 conscripts.
Main Battle Tanks - 800, although many are thought to be inoperable.
Armoured Infantry Fighting vehicles - 1,000.
Armoured personnel carriers - 945.
Artillery pieces 2,421
Air Defence surface-to-air missiles - More than 400.
NAVY - Numbers: 8,000. Two patrol submarines, which might both be out of action. Three surface vessels and 16 patrol and coastal ships.
AIR FORCES Numbers: 18,000. Combat capable aircraft - 394 (A mixture of Russian and French aircraft, many non-operational or in store) French Foreign Minister Alain Juppe said on Tuesday that only 20 were operational.
Air Defence Command has at least 216 surface-to-air missiles and 144 towed and 72 self propelled missiles. Maintenance may be an issue. Most analysts believe Libya's armed forces could not seriously threaten outside air forces enforcing a no-fly zone.
Sources for Libyan military: Reuters/IISS Military Balance 2011. (Reporting by Catherine Bremer in Paris, Keith Weir in London; Additional reporting by David Cutler; Editing by Jon Boyle)