It didn’t take long for well-meaning members of Congress last week to come up with an easy sounding proposal to help the Libyan opposition topple Moammar Gadhafi: Just impose a no-fly zone.

“We spend $500 billion on defense and we can’t take down Libyan air defenses?” Sen. John McCain, R-Ariz., told the Washington Post. “You tell those Libyan pilots that there is a no-fly zone, and they are not going to fly.”

Sen. John F. Kerry, D-Mass., chairman of the Senate Foreign Relations Committee, agreed. “A no-fly zone is not a long-term proposition ... and I believe we ought to be ready to implement it as necessary.”

But there’s one thing those optimistic assessments play down: Imposing a no-fly zone is an act of war, and we’re already at war in Iraq and Afghanistan.

If the United States sent aircraft to patrol the skies of Libya, the first step would have to be to knock out the country’s antiaircraft batteries; that’s an act of war too.

And any time the United States is at war ― even at the limited level of a no-fly zone ― the question of further military involvement often follows.

That dilemma helps explain why top civilian and military officials of the Obama administration sounded so unenthusiastic about the idea of a no-fly zone.

“It’s an extraordinarily complex operation to set up,” warned Adm. Michael G. Mullen, chairman of the Joint Chiefs of Staff.

“We also have to think about, frankly, the use of the U.S. military in another country in the Middle East,” added Mullen’s boss, Defense Secretary Robert M. Gates.

“We’re a long way from making that decision,” agreed Secretary of State Hillary Rodham Clinton, who noted that other countries in the area don’t favor Western military intervention.

To McCain, those statements sounded like excuses. “I think they are making up reasons” not to act, he said.

He’s right; they’re making excuses. And that’s a good thing ― at least as long as Libya’s air force isn’t gunning down unarmed civilians.

As no-fly zones go, an operation over Libya could be organized fairly quickly. The United States and its NATO allies already have airplanes, ships and radar in and around the Mediterranean, along with an airbase on Sicily, about 350 miles north of Tripoli.

The real reason for caution is the one Gates alluded to: We don’t need another war if we can avoid it.

A look at three recent no-fly zones shows how difficult it is to keep such an operation brief and limited.

After the Persian Gulf War in 1991, the United States and its allies imposed a no-fly zone over Iraq in hopes that it would help lead to Saddam Hussein’s downfall. It didn’t. But it did tie up aircraft and crews for more than a decade, and it led to the loss of two U.S. Black Hawk helicopters and their crews, shot down by U.S. F-15 fighters in a mistaken-identity incident in 1994.

In 1993, the United Nations imposed a no-fly zone over Bosnia-Herzegovina; as part of that operation, U.S. fighters shot down four Serbian planes. The Bosnian war ended in a U.S.-brokered peace agreement ― a success story for American diplomacy ― but it also led to the deployment of U.S. peacekeeping troops in Bosnia for more than eight years.

In 1999, NATO intervened against Serbia again over the disputed province of Kosovo, a campaign that went beyond a no-fly zone to target Serbian military installations on the ground. Then-President Clinton sought to limit U.S. military action to the air, but when it appeared that the campaign might not succeed, his aides drew up a plan to send ground troops ― one they never had to implement.

President Obama is in a difficult position. He has formally endorsed an international “responsibility to protect” ― the concept that if civilians are being massacred by their government or anyone else, the United Nations should step in to stop the bloodshed.

And in his 2009 Nobel Peace Prize speech, the president said: “When there is genocide in Darfur, systematic rape in Congo, repression in Burma, there must be consequences. Yes, there will be engagement; yes, there will be diplomacy; but there must be consequences when these things fail.”

But the consequence doesn’t have to be a no-fly zone ― at least, not in the full-scale form that was imposed in Iraq, Bosnia and Kosovo.

Administration officials say they are looking at a wide range of other options to dissuade Libya’s air force from attacking civilians. Military experts say those could include long-distance attacks against Libya’s airbases and the provision of antiaircraft weapons to anti-Gadhafi groups.

If the Libyan opposition forms a government and appeals for foreign help, that will quickly increase pressure on the administration and its allies to act.

The alternative ― standing by and ignoring the opposition’s pleas ― won’t be tenable for long.

It wouldn’t be good politics, either, to pass up an opportunity to help a new and friendly government come to power.

But it’s also worth counting to 10, slowly, before starting any war.

By Doyle McManus

Doyle McManus is a columnist for the Los Angeles Times. ― Ed.

(Los Angeles Times)

(McClatchy-Tribune Information Services)