Syrian President Bashar El Assad, left, greets Egyptian President Hosni Mubarak in Damascus, Syria, in March, 2005. Assad continues to stand his ground in the face of opposition of the type that drove Mubarak from office a year ago.

BEIRUT — Washington has warned Syrian President Bashar Assad that his days are numbered, but it now faces the vexing problem of how to dislodge a defiant leader intent on snuffing out the 11-month uprising against him.

One option increasingly under consideration is arming the rebels; another is to just look the other way should its Persian Gulf allies do so.

On Tuesday, the Obama administration said it would not support giving weapons to the Syrian opposition — for now, at least — despite calls from some congressional leaders to do so. Washington said its current focus is to organize a “contact group” to build stronger ties with the Syrian opposition and pressure Assad with tightened economic sanctions.

But diplomats acknowledge privately that although this effort has value, it is likely to have limited impact even as the Syrian death toll continues to rise.

Meanwhile, Assad stood his ground Tuesday, welcoming Russia’s foreign minister to Damascus. Pro-government demonstrations took place in the country’s two biggest cities, ostensibly staged to thank Russia and China for their weekend veto of a U.N. Security Council proposal calling on him to cede power.

Faced with limited options, Western powers and their Arab League allies have begun “trying to decide what to do about support for the armed opposition,” said Andrew Tabler, a longtime Syria analyst at the Washington Institute for Near East Policy. “This discussion is going to suck everybody in.”

Syria’s singular geopolitical importance renders the outcome of its rebellion potentially more disruptive that that of other “Arab Spring” upheavals. Syria borders Israel, wields great influence in Lebanon and is a patron of the Islamic militant group Hezbollah.

Perhaps most critically, Syria is not isolated. One key ally is Iran, which is suspected of seeking nuclear arms capabilities while locked in a bruising battle for regional dominance with rival oil producer Saudi Arabia, a close U.S. ally. The Syrian government also has support from neighbors Iraq and Lebanon.

As such, an armed struggle to oust Assad is likely to be protracted and bloody, with nasty sectarian overtones, analysts say. It could also involve alliances with Islamic militants and others whose view of a future Syrian society may be directly at odds with the concept of a Jeffersonian democracy.

Experts foresee the possibility of a long-term proxy war, with gulf state money funding arms for Syrian rebels in an updated version of the 1980s battle for Afghanistan, when the West and Arab allies bankrolled an uprising against a Soviet-installed secular regime.

The fight for Syria has already revived a Cold War trope: Russia backs and arms the government in Damascus, whose ouster is sought by Washington and its allies in Europe, the Arab world and Turkey, an emerging regional powerhouse that has turned on Assad.

“In Syria you have three layers: a global struggle, a regional struggle and an internal struggle,” said Rami Khouri, director of the Issam Fares Institute for Public Policy and International Affairs at the American University of Beirut.

Syria’s sectarian subtext — a majority Sunni Muslim population seeking to free itself from the yoke of Assad’s minority Alawite sect, an offshoot of Shiite Islam — raises disturbing comparisons to the bloody sectarian warfare that consumed neighbors Iraq and Lebanon. Minorities, including Alawites and Christians, are terrified that an intolerant, Muslim Brotherhood-led government would emerge from the ashes of the Syrian regime led by the Assad family for four decades.

So far, U.S., European and Arab states have endorsed an expansion of the approach of squeezing Assad via nonlethal means: by toughening economic sanctions, bolstering overtures to the fractious Syrian opposition and seeking to broaden Syria’s diplomatic isolation.

U.S. officials say they have no immediate plans to provide security aid to the Syrian rebels but are taking no option off the table. “We are not considering that step right now,” Jay Carney, the White House press secretary, said Tuesday.

But diplomats acknowledge privately that the nonmilitary strategy is likely to only alter Assad’s behavior slowly at best, even as the body count from his crackdown on dissent continues to rise. Thus, the question of whether to provide intelligence help, arms and money to rebels is assuming a growing urgency.

Among the voices calling for a tougher approach against Assad on Tuesday was U.S. Sen. John McCain, R-Ariz. “We should start considering all options, including arming the opposition,” said the 2008 presidential candidate. “The bloodletting has got to stop.”

Whether arming the opposition would increase or reduce bloodshed, however, remains unclear.

Advocates for military aid say that, whether the West likes it or not, the fight is lurching toward civil warfare — and defeat of the insurgents would squander the strategic gains made by the opposition.

Some arming of the opposition “is going to be happening in any case, because there are a lot of people in the gulf who see a lot of advantages in accelerating what’s going on in Syria,” said John P. Hannah, who was national security adviser to Vice President Dick Cheney. “There’s an argument to be made that the U.S. and the West should figure out some way to gain influence on this, to ensure that it plays out in the way that best advances U.S. interests.”

Options, he said, include maintaining intelligence contacts with the rebels and providing satellite imagery, medical assistance, nonlethal hardware or arms.

Several diplomats and analysts said they believe the mostly likely outcome is that Persian Gulf states, perhaps Qatar or Saudi Arabia, will quietly arm the rebels while the United States looks the other way.

Another possibility is that the Gulf states will refrain from providing security help, but rich individuals from the gulf will decide to do so instead.

Such tactics, critics say, would confirm the Russian and Syrian arguments that the Western and Arab goal all along has been a change of government. It would also undermine any Western mediating role and risk having the conflict turn into a full-blown proxy war pitting outside powers against each other.

Calls to arm the opposition are being voiced in the Western-Arab-Turkish alliance, diplomats say, though they add that the various capitals are still far from embracing the idea. Turkey said Tuesday that it was planning a new initiative in conjunction with its allies after Prime Minister Recep Tayyip Erdogan labeled the U.N. veto “a fiasco for the civilized world.”

One option floated in some circles is the creation of “buffer zones” for Syrian civilians fleeing warfare near the Turkish-Syrian border, though Damascus would probably view such a move as an act of war.

On the diplomatic end, a top goal of the new “contact group” would be to help organize the opposition, whose internal squabbles and increasingly militarized presence have alienated many middle-class Syrians. Merchants and others wonder whether a rebel victory would result in chaos or preserve rights for minorities and a state with functioning institutions.

“They need to show that their future is not what Iraq looked like in 2006,” said one Western diplomat, a reference to the sectarian fighting that raged there at the time.

McDonnell reported from Beirut and Richter from Washington. Staff writer Lisa Mascaro in Washington and special correspondent Rima Marrouch in Beirut contributed to this report.

