Western leaders know NATO jets could easily force Moammar Gadhafi's few dozen Cold War-era warplanes from the skies and rob the Libyan dictator of a powerful weapon against rebels trying to oust him. But they're wary of involvement.
Imposing a no-fly zone from a string of Mediterranean bases and aircraft carriers could become a complex, long-term commitment for the U.S. and its allies. It would require airstrikes on Gadhafi's anti-aircraft weapons and risk drawing the West into another grueling military conflict in the Muslim world.
The Libyan rebels, who lack planes, have pleaded for such a zone _ a plan endorsed by Britain, France and some key U.S. lawmakers. But NATO nations appeared torn Wednesday between the desire for action and fears of unintended consequences in a conflict that has divided Libya and driven oil prices to 2 1/2-year highs.
The White House said a meeting of President Barack Obama's top security advisers would not result in an immediate decision on U.S. action. NATO said it was planning for "all eventualities" but gave little sign of moving to set up a no-fly zone.
"NATO is not looking to intervene in Libya," NATO Secretary General Anders Fogh Rasmussen said.
Although many nations want to tip the balance of military power away from Gadhafi, protecting civilians would be the key public rationale for any no-fly arrangement.
A senior U.S. official in Brussels said a no-fly zone would be "a difficult, costly and large operation," and noted that there was no evidence of any large-scale bombardment of civilians. He spoke on condition of anonymity because of the sensitivity of the issue.
U.S. Defense Secretary Robert Gates observed last week that attacking Libyan air defenses would be necessary before imposing a no-fly zone, and would be tantamount to war. Gadhafi has warned of retaliation against no-fly patrols.
Weighing heavily on the debate are the lessons of Iraq and the Balkans, where no-fly zones lasting years were credited with preventing much bloodshed in the 1990s but still did not stop some massacres.
The U.S., France and UK declared no-fly zones for fixed-wing aircraft after the 1991 Gulf War in order to protect Kurds in Iraq's north and Shiites in the south from Saddam Hussein's air force.
However, Saddam circumvented them by using helicopters to devastating effect when he hunted down dissenters through marshes while putting down protests across southern Iraq, said Michael Rubin, a Middle East scholar at the American Enterprise Institute, a conservative U.S. think tank.
Rubin, who advocates a no-fly zone over Libya to protect civilians, says the ban must include helicopter flights.
Other U.S. experts have cited the Iraq experience as an argument against a no-fly zone.
"The no-fly zone remained in place for about 12 years without forcing change in Saddam's policies," George Friedman, CEO of the Stratfor intelligence analysis group, wrote in a recent report. "The same is likely to be true in Libya. The no-fly zone is a low-risk action with little ability to change the military reality that creates an impression of decisive action."
And such a zone might fail to eliminate one of the major threats from the air.
Gadhafi has between two and three dozen Russian-built Mil helicopter gunships, some of which have mounted the deadliest known attacks against the rebellion. The fast NATO fighter jets would have a hard time detecting and targeting the slow-moving, ground-hugging helicopters.
After ethnic fighting erupted in Bosnia, the U.N. Security Council ordered a no-fly zone in 1992 to protect areas under government control from strikes by rebel Serbian jets.
Allied interceptors shot down four Serbian attack jets, but the zone failed to stop fighting on the ground. In the bloodiest incident, Serbian troops overran the government-held enclave of Srebrenica and massacred 7,000 captured soldiers and refugees in the worst slaughter in Europe since World War II.
A no-fly zone requires complex planning on legal authority, rules of engagement and details on how much territory it covers and during what times of day, said David Deptula, a retired U.S. lieutenant general who oversaw a no-fly zone over northern Iraq after the 1991 war.
"This isn't just sending a bunch of airplanes to shoot down other aircraft," he said.
The zone need not span all of Libya, one of Africa's largest countries, because much of the fighting has been confined to its coastal strip.
NATO and the U.S. say they would not act without U.N. Security Council authorization, and Western diplomats have said a Britain- and France-backed resolution to impose a no-fly zone won't be introduced to the council unless it is endorsed by the Arab League and the African Union at meetings in coming days.
Gadhafi's pilots would almost certainly be routed if they tried to flout a Western flight ban.
Since the 1990s, poor maintenance and lack of funding have shrunk Gadhafi's fleet of more than 400 fighter-bombers, light attack jets and helicopter gunships to a few dozen aircraft. What remains are mostly Sukhoi Su-22 and Mig-23 fighter bombers and Yugoslav-made Jastreb light strike jets dating from the late 1960s. Several have been destroyed by the insurgents, or been flown out of the country by pilots defecting from Gadhafi's forces.
The government has only a handful of planes designed to intercept other aircraft, the Mig-21 and Mig-25, also dating from the 1960s.
NATO officials say they could quickly deploy 200-300 jets to Libya from bases stretching from Gibraltar to Greece, and from U.S. carriers in the Mediterranean.
These would include top-of-the-line Eurofighter Typhoons used by the British, Italian and Spanish air forces. Also available are the formidable French Dassault Rafale fighter and the U.S. Boeing Co.'s F-18 Super Hornet, the backbone of U.S. Navy air power.
The alliance also would have a huge advantage in its AWACS planes _ whose rotating radars can look 200 miles (320 kilometers) deep into enemy airspace, monitor all aerial movements over Libyan territory and direct planes to any violators of the no-fly zone.
They also are equipped with the latest air-to-air missiles, which are far more sophisticated than the Soviet-built models of the 1980s in the Libyan arsenal.
Rebecca Santana in Baghdad and Edith M. Lederer at the United Nations contributed to this report.