Russia is reported to have recently shipped Buk-M2 missiles, like the one displayed above, to Syria. (Mikhail Metzel/AP)

The Syrian government’s downing of a Turkish fighter jet has served as a stark warning that its military is capable of mounting a sophisticated defense against potential enemies, complicating a Libya-style intervention.

Turkey has said that it has no immediate plans to respond to the incident with military action. But the Turkish prime minister warned Tuesday that he had ordered commanders along the country’s southern border to treat any Syrian military approach as a threat, escalating concerns that Turkey — along with the United States and its allies — could be drawn into a regional war.

Details of the plane incident along the Syrian coast are still emerging, but officials said Syria beefed up its air defenses with purchases from Russia after Israeli fighter jets destroyed a nuclear reactor under construction in the Syrian desert nearly five years ago. At least on paper, U.S. military officials said, the Syrian air defenses appear to be far more robust than those encountered by NATO in Libya and stronger than even Iran.

“I can name you worse [systems], but they are in places like China,” said an Air Force official, who spoke on the condition of anonymity because he was not authorized to discuss the matter publicly.

Concerns about the capability of the Syrian military are only one reason that the international community has refused to intervene in President Bashar al-Assad’s bloody crackdown on opposition groups.

But defense officials and military analysts say defeating Syria’s air defenses would require a sustained U.S. military effort, which would probably lead to civilian casualties.

Those urging caution warn that any military action risks plunging Western forces into the middle of what is essentially a sectarian civil war that could spread throughout the region.

At a time when the U.S. military is still fighting in Afghanistan and recovering from the long, bloody occupation of Iraq, there is also resistance inside the Pentagon to using force in instances in which U.S. national interests are not directly threatened.

“We can deal with the Syrian integrated air defenses,” said retired Lt. Gen. David Deptula, who oversaw Air Force intelligence efforts in the Pentagon. “It is much, much more challenging than Libya. They have some of the most recent surface-to-air missiles out there. But before we address the how, we need to address the why.”

In the wake of the 2007 raid by Israel on the al-Kibar nuclear reactor, Syria spent billions of dollars to upgrade its 1960s- and 1970s-era missile defenses. Among those purchases was the SA-22 Pantsir armored rocket system, which some defense officials speculated may have been used against the Turkish jet.

“The [Israeli] strike prompted the Syrians to purchase some very capable Russian systems,” said Douglas Barrie, a senior fellow specializing in aerospace at the Institute for International Strategic Studies in London.

Many defense analysts said the Syrian system is similar to Iran’s air defenses in terms of technology, but they suggested that the Syrian version is more effective because it is concentrated in a smaller area.

(Gene Thorp/The Washington Post)

“The Iranians have a huge geographic area to cover, which creates gaps that you can fly through and around,” said Jeffrey White, a fellow at the Washington Institute for Near East Policy and a former Defense Intelligence Agency analyst. “The Syrian system is much more dense.”

The Syrian air defenses are also more tightly integrated than the Iraqi or the Libyan systems, allowing Syrian military officers at disparate sites to share targeting information gleaned from radar.

Even a relatively sophisticated air defense system has potential weaknesses, however. Although the Syrian system looks good on paper, it’s not clear that the Syrians have the trained personnel who can operate it effectively, analysts said. U.S. officials said they are also unsure whether the Syrians can maintain and repair the system.

The U.S. and NATO forces would also employ jammers and other sophisticated technology to disrupt Syrian radar and communications systems that were not in use by the Turkish aircraft.

Turkish officials said their jet mistakenly entered Syrian airspace near the port of Latakia but quickly left after being warned by a Turkish radar operator of the error. The Turks said they lost radio contact with the jet about 13 miles from the Syrian coast.

The aircraft, which carried photo surveillance equipment, could have been watching the Syrian port for arms shipments.

U.S. officials said it is still unclear exactly what the Turkish jet was doing and where it was relative to Syrian territory when it was downed. “There are a lot of unknowns,” a senior U.S. military official said.

In the wake of the attack, Prime Minister Recep Tayyip Erdogan vowed to take military action against any “element that approaches the Turkish border from Syria in a way that may pose a risk or danger.”

Syria’s most sophisticated air defense systems are concentrated along its southwestern border to guard against an Israeli incursion. An international effort to create a no-fly zone for rebels and refugees along the Turkish border would not necessarily have to contend with the most sophisticated Syrian systems.