The last thing the United States needs at the moment is to get involved in another Mideast war.

So some may hope a shaky truce in Syria, brokered last week by former U.N. Secretary-General Kofi Annan, can halt the regime’s vicious slaughter of civilians. Some may even hope the Annan plan will defuse a Syrian conflict that could drag in NATO forces.

Sorry to say, those are unrealistic hopes.

After months of watching Syrian artillery pound residential neighborhoods, courtesy of gritty video on YouTube, we should understand the basics: Bashar al-Assad won’t willingly end his family’s 40-year dictatorial reign.

The U.N. plan called for Assad to pull back troops and heavy weapons from cities, and permit peaceful demonstrations — as a prelude to talks about a political transition. But the tanks, artillery, and snipers remain in place, although they were relatively restrained on Friday when crowds poured out after prayers.

That regime’s restraint is unlikely to last. “We know Assad will never respect the Annan plan because he knows the response will be millions on the street,” says Radwan Ziadeh, the U.S.-based spokesman for the opposition Syrian National Council.

“What we have is a cease-fire light,” says Andrew Tabler, author of “In the Lion’s Den: An Eyewitness Account of Washington’s Battle with Syria.” “I don’t think it will hold.”

Yet the reason so many place their hopes in the Annan plan is because the other options are so grim.

One oft-heard option, advocated by Sens. John McCain, R-Ariz., and Joe Lieberman, I-Conn., among others, calls for arming the Syrian opposition and setting up a safe haven inside Syria, adjacent to the Turkish border. This no-fly zone, where opposition fighters could gather, would be protected by NATO planes.

Those who advocate a no-fly zone never explain how it would lead to the fall of Assad. Consider the following:

A large segment of the Syrian population still backs Assad because it worries that chaos will follow his downfall. Syria’s large Christian minority, along with middle-class merchants, senior bureaucrats, and Baath Party members, fear a repetition of what happened in Iraq after Saddam Hussein’s ouster: the rise of Islamist parties, the persecution of Christians, and the purge of secular civil servants and academics.

Moreover, the Syrians who have taken up arms (after the failure of peaceful protests) are no match for Assad’s well-armed forces. The Syrian officer corps and key special units remain loyal because they belong to Assad’s Alawite (Shiite) religious sect. Alawites make up 10 percent of a population that is predominantly Sunni, and they view their survival as tied to the regime.

Furthermore, Syrian forces are armed by Russia, which is still backing Assad, whose security apparatus is also trained by Iran’s Revolutionary Guards.

If NATO agreed to protect a no-fly zone along the Turkish border it would inevitably be sucked deeper into the Syrian conflict elsewhere in the country. NATO would also find itself in opposition to Russia. No wonder President Obama (and Turkey) have been reluctant to endorse such a zone.

But the Annan plan’s slim prospects shouldn’t lull anyone into thinking hard choices can be avoided for much longer. The cease-fire will fail, and the fighting will go on.

Meantime, Saudi Arabia is starting to funnel funds to the opposition. The longer and bloodier the Syrian battle, the more likely radical Islamists will rise to lead the opposition. When Assad falls, the West (and Israel) will face an unpredictable Islamist regime.

What is to be done? Washington, its NATO allies, and the Arab League should use the current, brief lull to focus on two crucial efforts:

First, undertake a full-court press to awaken Russian leaders to the imminent danger Assad presents to Moscow.

On a recent visit to Moscow, I heard repeatedly that Russian President-elect Vladimir Putin believes Assad will surmount his troubles. The killing of Syrian civilians does not trouble Putin.

The Russian leader’s main concerns are two: a stable Syrian regime that will buy Russian arms, permit Russia to use Tartus port, and keep Syrian Islamist movements down. With his own political future in mind, Putin is also deeply opposed to the ouster of Russia’s last Mideast ally by a revolution from below.

To meet Putin’s concerns, NATO and Arab leaders must convince Moscow that Assad’s survival is unlikely, and that the only way to avoid Russia’s nightmare scenario is for Moscow to press him go peacefully, and soon.

But NATO and Arab leaders must also urge the Syrian opposition to agree on a clear, and inclusive road map for unifying the country. The fastest way to force Assad out would be to win over a broader swathe of Syrians — including Christians, businessmen, and respected Sunni leaders. That would split the regime from within. Then pressure would mount from inside the system to oust him.

And NATO would be saved from stumbling into another Mideast war.