MOSCOW (AP) — When Syria broached the possibility of using chemical weapons, the world's response was don't even think about it. But one voice in that chorus mattered more for Syrian ruler Bashar Assad: Russia, his key ally.

Russia has been Syria's key protector throughout the 16-month uprising that evolved into a full-blown civil war, shielding Assad's regime from international sanctions and providing it with weapons despite an international outcry. And after the opposition attack last week that killed four members of his inner circle, the Syrian strongman may have to seriously think about a getaway scenario, for which Russia's help will be essential.

"Assad can't afford not to listen to Russian signals," said Fyodor Lukyanov, the editor of Russia in Global Affairs magazine. "He understands quite well that if he angers Russia, it will step back, leaving him to his doom."

Lukyanov and other analysts say that Russia is maintaining a constant dialogue with Assad and warning him against crossing red lines, but its clout is limited.

"Russia certainly can't force Assad to step down," Lukyanov said. "What Russia can do is to tell him what are the limits he can't cross, and it has been doing that. It may tell him that if he uses chemical weapons that would mean his end."

He said that the Russian statement Tuesday regarding the Syrian chemical weapons threat also appeared to be an attempt to contain the damage the Syrian regime inflicted on itself.

Earlier this week, the Assad regime announced that it has chemical weapons and would use them in case of foreign aggression. Lukyanov and other Russian analysts said Assad's regime doesn't appear to intend to resort to its chemical arsenals. But some warned that Assad would be likely to step up military action.

Igor Korotchenko, a retired colonel of Russia's military general staff who is now editor of National Defense magazine, said that Assad could use heavy weapons against rebel-held areas, imitating Russia's action during two separatist wars in Chechnya.

"That's his only chance for retaining control over the country," Korotchenko said.

Despite occasional criticism of the Syrian ruler for excessive use of force and failure to launch reforms, Russia has placed its bets squarely on Assad's survival and shown no inclination of dropping its support for the strongman.

A squadron of Russian navy ships, including several assault vessels carrying marines, is heading toward the Syrian port of Tartus, the only naval base Russia has outside the former Soviet Union.

"Its mission is to evacuate Russian citizens if the situation worsens," Korotchenko said. "It's also a demonstration that Russia is a key player in the Middle East and a signal that there should be no foreign military interference in Syrian affairs."

Alexander Shumilin, the head of the Moscow-based Center for Analysis of Mideast Conflicts, said the Syrian statement about possible use of chemical weapons in case of a foreign attack reflected chaos and desperation in Assad's inner circle and further weakened his positions.

He said the Russian Foreign Ministry statement that reminded Assad of his international obligations sent a strong warning to Damascus that using chemical weapons would be suicidal. "That would mean crossing the red line and make Russia look like an accomplice," he said. Continued...