Despite U.S. protests, Russia is supplying Arab ally Syria with "defensive weapons" the Moscow insists have no relevance to the Damascus regime's brutal efforts to crush a 15-month-old pro-democracy uprising.

That may well be true -- for now, at least.

But most of the Russian weapons systems -- including upgraded MiG-29 interceptor jets, BUK-M2E air-defense missiles, Bastion costal defense batteries armed with supersonic anti-ship cruise missiles -- ensure that any Western-led military intervention to halt the Syrian bloodbath would be costly.

"I would like to say these mechanism are really a good means of defense, a reliable defense against attacks from air and sea," Anatoly P. Isaykin, general director of Russia's state arms exporter Rosoboronexport, told The New York Times last week after U.S. Secretary of State Hillary Clinton accused Moscow of shipping attack helicopters to Syria.

"This is not a threat but whoever's planning an attack should think about this," Isaykin said.

There seemed little doubt that Isaykin's comments were intended to warn off the Americans, British, French and others who increasingly see military intervention to be necessary to head off a full-blown civil war in Syria that could ignite neighboring Lebanon, Iraq and Jordan.

Moscow, Syria's main arms supplier during the Cold War, has become the principal protector of Syrian President Bashar Assad's minority regime as part of Russian President Vladimir Putin's drive to re-establish Moscow as a pivotal player in the Middle East.

"Russian leaders will use the Syrian crisis as an opportunity to show that their country is still a force to be reckoned with in the Middle East," Oxford Analytica observed in a recent report.

"They will also press their case that overthrowing the current Syrian regime would lead to further instability in the region -- which might even spread to the former Soviet Union.

"As a result, Russia will do its utmost to prevent the fall of President Assad," Oxford Analytica concluded.

Thus, it's instructive to look at what weapons systems the Russians have shipped to Syria, one of the top five purchasers of Russian weaponry, over the last couple of years. These included:

-- 2,000 anti-tank missiles for Syria's aging but upgraded T-72 tanks. Some 800 tanks have already been upgraded under a $500 million contract.

-- 200 SA-17 surface-to-air missiles, usable only on ships, helicopters and vehicles, delivered without shoulder-fired launchers due to U.S. and Israeli pressure. Israel says two batteries have been deployed along the Lebanese border, while a third is in training.

-- 36 Pantsir S-1E mobile air-defense systems, armed with 500 SAMs.

-- Two K-300 Bastion coastal defense batteries armed with an estimated 73 Yakhont supersonic anti-ship cruise missiles capable of knocking out large vessels. The Syrians have already tested these batteries.

-- In January, Syria signed a $500 million deal to buy 36 Yak-130 advanced jet training aircraft built by Russia's Irkut Defense Corp. that can also double as light attack aircraft, usually as part of Russian armored divisions. Deliveries are expected to start in 2013.

Since Syrian insurgents don't have tanks or aircraft, of these systems, only the Yak-130 could be considered useful to the regime in combating insurgent forces.

Syria's main adversary in the region is Israel, its southern neighbor, and considered the overwhelming military force in the Middle East.

There are other military contracts systems that Syria is pursuing with Russia. They're worth an estimated $4 billion and include:

-- Modernization of the final 200 T-72s under the $500 million contract with Russia to upgrade 1,000 of the tanks.

-- 200 more SA-19 air-defense missiles, more SA-18 Iglas, and eight BUK-M2E air-defense missile batteries worth $1 billion.

-- Supersonic 9M123 Chrysanthemum self-propelled anti-tank missile systems made by Russia's KBM.

-- Upgrading 24 MiG-29s, and S-125 Pechora-2 surface-to-air missiles.

These sales are vital for Russia's defense industry, a vast enterprise during the Cold War but now much-reduced and, like every other defense industry, heavily dependent on exports to maintain production lines.

Russia also doesn't want to lose its naval maintenance base at the Syrian port of Tartus, its only military facility outside the former Soviet Union and its only foothold in the Mediterranean.

A visit by a Russian naval flotilla headed by the aircraft carrier Admiral Kuznetsov in January was seen as a display of Russian support for Assad's embattled regime.