Russia's only operational aircraft carrier and other warships are visiting the Syrian port of Tartous in an apparent display of support for beleaguered President Bashar al-Assad.

The high-profile Russian move will provide the increasingly isolated Assad with a psychological boost as he battles to save his dictatorial regime from a surprisingly stubborn 10-month-old popular uprising.

But the visit, which Russian officials insist had been planned for months and is not linked to the Syrian crisis, came amid signs the uprising was sliding into a sectarian civil war that could have serious repercussions across the Middle East.

The more militant of the opposition forces arrayed against Assad's regime have stepped up calls for United Nations, NATO or other foreign military intervention to prevent a bloodbath on an epic scale.

The arrival in Tartous of the Russian flotilla Sunday followed the recent deployment of the nuclear-powered U.S. aircraft carrier USS George H.W. Bush in the eastern Mediterranean off the Syrian coast.

The Obama administration has denounced the bloodletting in Syria, Iran's key Arab ally, and Assad's brutal use of his security forces.

Washington and its allies want to pry Syria away from the Iranians and sever Tehran's logistic links via Syria with Hezbollah, Iran's powerful proxy in the Levant.

Despite strong Western criticism, Russia has stood by its former Cold War ally in the face of mounting international condemnation of the Syrian regime for unleashing its security forces to crush the relentless anti-government protests.

By U.N. count, at least 5,000 people have been killed since March 15, 2011. Assad claims the uprising is a "foreign conspiracy."

There was no evidence of that in the revolt's initial stages, but that's unlikely to be the case now as world opinion, and Arab opinion particularly, has turned solidly against the hard-line Damascus regime.

Turkey, Syria's northern neighbor, in particular has been aiding Syrian army defectors who have formed the Syrian Free Army.

There are increasing signs that Syria's opponents are funneling arms into the country for Assad's opponents. Qatar is reported to have recruited 2,000 Arab mercenaries to aid the Syrian opposition.

This is causing deep concern in Lebanon, long under Syria's thumb, where the regime has many allies, most notably the heavily armed Hezbollah.

With Assad, whose minority Alawite regime still retains the loyalty of its powerful security apparatus and key elements of the Russian-armed military, showing no sign of throwing in the towel, the crisis seems doomed to worsen.

In Assad's fourth public appearance since the uprising began, he declared during a speech before a handpicked audience of loyalists at Damascus University he will never stand down.

Claiming he has "the support of the people," he vowed, "We will declare victory soon."

The Russian flotilla's arrival in Tartous for a six-day visit was widely seen as a message from Moscow to the West: Do not interfere the way you did in Libya through NATO to bring about the fall of longtime dictator Moammar Gadhafi, a former Soviet ally.

Moscow's Izvestia newspaper quoted Adm. Viktor Kravchenko, Russia's former Chief of Naval Staff, as saying the flotilla's presence in the eastern Mediterranean "will prevent the outbreak of an armed conflict."

The Russian ships were led by the 43,000-ton carrier Admiral Kuznetsov, which carries a score of Sukhoi Su-33 and MiG-29K fighters and two Ka-27 anti-submarine helicopters.

The developments in Syria are linked to the confrontation in the Persian Gulf between Iran and the United States, backed by its Arab allies in the oil-rich region.

So what transpires in Syria could have a significant impact on what happens in the gulf, particularly in terms of Tehran's ability to cause turmoil in the region.

Iran has threatened to close the strategic Strait of Hormuz, through which one-fifth of the world's oil supplies pass every day, if the United States and Europe tighten sanctions imposed in June 2010 by throttling Iran's vital oil exports.

Shutting the oil artery, even for a week or two, would send oil prices soaring -- some analysts predict as high as $250 a barrel -- and cause global economic distress.

In Syria, the Arab League has boosted the number of observers it deployed in December, with Damascus' grudging approval, to 165.

But that's far too few to effectively keep tabs on the regime's actions as the uprising turns increasingly violent. More bloodshed seems inevitable.