an uprising among the majority Shi'ite population for which Riyadh has blamed Iran.

Iran's various leaders, on the other hand, while appearing to distance themselves somewhat from Assad's violence - and his unpopularity at home and abroad - seem unlikely to abandon their long-time ally, particularly at a time when they, too, feel threatened by popular frustrations at home and pressure abroad.

Western adversaries of Iran have accused it of supplying not just military equipment but electronic surveillance and other tools developed to crack down on dissidents using the Internet and mobile phones. Assad's enemies accuse him of using Iranian specialists to help against the revolt and rebels say they have captured a handful of Iranian military personnel inside Syria.

There are suggestions that Iran's Revolutionary Guards - and their Lebanese allies in Hezbollah - may have provided some of the sharpshooters picking people off on the streets of Homs.

This week, two Iranian warships docked at a Syrian port in what looked like a show of military support, according to Iran's Press TV. The Pentagon said it had no indication the ships had docked.

Directly on his eastern and western borders, Assad also has friendlier faces - Iraq's Shi'ite-led government is at least ambivalent, while in Lebanon, where Hezbollah has emerged as a dominant force in the years since Assad pulled Syrian troops out of his smaller neighbour, Assad has clear support.

Lebanon stood out by opposing an Arab League resolution in November that called for Assad to step aside. In that vote, Iraq abstained. Last week at the United Nations, as pressure mounted, Iraq voted against Assad, while Lebanon was among abstainers.

To the south, Jordan, like the Gulf powers another Western-allied Sunni monarchy, has come out publicly against Assad. But with concerns for its own stability, it seems unlikely to take a strong lead in backing the rebels beyond accepting refugees.

The other southern neighbour Israel, which has occupied the Golan Heights since seizing them from Syria in the war of 1967, has been unenthusiastic about the possible chaos or Islamist takeover that might follow a departure of its old, but generally subdued, enemy, the Assad administration.

However, it appears to have concluded it cannot survive, and is planning for change, as well as an influx of refugees heading for the Golan, which is home notably to communities of Druze.

In a turn that may demonstrate a shifting balance of power in the region, the Palestinians' Sunni Islamist movement Hamas has distanced itself from Assad, moving their leader out of Damascus and, after two decades of backing from Iran, Syria and Hezbollah, it is sounding out support from Sunni Qatar.

Egypt, the most populous Arab state, where the Sunni Islamists of the Muslim Brotherhood now dominate a parliament elected after the overthrow of Hosni Mubarak last year, is also looking kindly on its fellow Brotherhood followers in Syria.

Assad's northern neighbour, Turkey, a Muslim NATO member whose leadership comes from a Sunni Islamist background, has also abandoned him, condemning a former friend and giving refuge to rebel commanders of the Free Syrian Army.

Ankara is worried a flood of refugees could destabilise the border. It has raised the possibility of creating safe areas in Syria to protect civilians, and even of intervening militarily if there were massacres in cities. Any action, though, officials say, would only be undertaken with some form of international mandate, including support from Arab and Western allies.

Friday's meeting in Tunis, at which Turkey hopes to take a lead after being slow off the mark to join NATO allies against Gaddafi, may offer clues as to how far Ankara is prepared to go.

COLD WAR

However impressive the anti-Assad bloc may be, a world power stand-off in the Middle East is becoming more defined and recalls the days of the Cold War, when Assad's father used a firm alliance with the Soviet Union against the United States to arm himself heavily against enemies internal and external.

Nostalgia may play little part in Moscow's strategy today, but Syria hosting Russia's only Mediterranean naval base, at Tartous, and the possibility of using the Syrian conflict to reassert itself as a diplomatic player in the region means that Moscow shows little sign of siding quickly with the West.

China, too, as seen in its sympathetic ear for Iran's leaders, has a growing interest, as an increasingly demanding consumer of energy, in asserting itself in the Middle East.

And, like Russia, Beijing has shown a commitment to blocking moves at the United Nations which, seen across the desks of leaders whose power rests as much on state control as popular choice, appears to give foreign powers a say in who rules.

Taken aback by the way a U.N. Security Council resolution which they failed to veto led to the Western military campaign that helped topple Colonel Gaddafi, Russia and China have made clear they will not allow any new move to give a licence for "regime change" in the name of Western-inspired democracy.

This week, Beijing's People's Daily told the West its calls for Assad to quit could provoke "large-scale civil war".

Russia's Vladimir Putin, campaigning to become president again in an election he is sure to win next month, has made a point of condemning as a "culture of violence" the temptation among Western governments to intervene militarily abroad.

Having first entered the Kremlin 12 years ago on the back of the bombardment of a Russian city, Grozny, that was in the hands, as he saw it, of Wahabbi Islamist rebels, Putin has little reason to condemn Assad's assaults on Homs or Deraa.

Syrian defectors, rebel forces, Russian analysts and international shipping data all indicate that Russia continues regular supplies of heavy armaments to the Syrian government - as it is legally entitled to do in the absence of any embargo.

While Iranian and Chinese arms form substantial parts of Assad's stocks - only a small proportion of which have yet been expended - Russia may account for nearly all of the newer, and more high-performance, equipment reaching Syria, both directly from Russian state-run firms and via middlemen, analysts say.

As in the Balkans, where Western backing for, say, Kosovo separatists, against Moscow's ally Serbia raised tensions to levels rarely seen since the Cold War, this places Moscow in direct confrontation with leaders in Europe and Washington.

In France, the former colonial power which drew modern Syria's borders, President Nicolas Sarkozy is highlighting his leading role in the Libyan war as he fights a tough campaign for re-election. He has been vocal in condemning Assad and supporting the disparate, often fractious, Syrian opposition.

NOT LIBYA

The United States, Britain and others have also pulled no punches verbally to denounce the "brutal dictator" Assad.

While British Prime Minister David Cameron has relished some of the credit for overthrowing Gaddafi, unlike Sarkozy and U.S. President Barack Obama, he does not face an election this year.

Some of Obama's Republican opponents in the Senate have already explicitly called for Washington to help arm the rebels, if only through Arab allies.

In a shift of emphasis, U.S. officials on Tuesday signaled that if Assad did not embrace a political solution to ease him from power the United States might have to consider alternatives to its policy against arming the opposition.

As in the Balkans, as over Iran, the realpolitik of a global power confrontation puts Syria in a very different situation from Libya, a geographically isolated, thinly populated, socially homogeneous state whose ruler's talent for shifting foreign alliances had deserted him and left him vulnerable.

Syria's population is four times that of Libya, jammed in to a tenth of the