Doha, Qatar - With little to show after months of diplomatic toil aimed at ending the fighting in Syria, the Obama administration has announced that the US will soon begin to send arms to opposition fighters.

As the US president's policy reversals go, this one was not entirely unexpected.

US officials said evidence that the Syrian regime had crossed the so-called red line of chemical-weapons use provided the immediate justification to act.

However, the timing of the announcement - just days after the military gains made by President Bashar al-Assad's forces with the help of Hezbollah fighters from Lebanon - could hardly have been a coincidence.

Now, as officials of the pro-opposition Friends of Syria Group gather here in Doha to consider the "moderate" Free Syrian Army's plea for heavy weapons, reports suggest Sunni Muslim fighters are streaming into Syria and new arms shipments are reaching both the FSA and Islamist rebels battling Assad's forces.

The developments are bound to intensify the debate about whether these weapons will spawn a new crisis by ending up in the hands of al-Qaeda-linked groups or level the playing field for the rebels in preparation for a negotiated political settlement.

The difference between a rapid resolution and indefinite continuance of the Syrian conflict is of much more than just hypothetical interest to several million Syrians, Lebanese, Palestinian refugees, Turks, Kurds, Iraqis and Jordanians living in the Middle East.

As far as they are concerned, "uncertainty is the only certainty" in their lives, and foreign arms consignments - regardless of their recipients - could make both the violence and the humanitarian crisis a lot worse in the short run.

Unpredictable course

What makes the conflict's course particularly unpredictable is that, unlike Iran and Russia, who are steadfastly determined to prevent Assad's conservative Sunni Syrian opponents from capturing power in Damascus, the attitude of the US administration and some of its European allies towards the rebels is ambivalent at best.

Explaining the rationale behind Obama's decision to arm the FSA directly, Mark Kimmitt, a former Bush administration official, said on Al Jazeera's Inside Syria programme: "The purpose… is not to create war but to force Assad to the negotiating table. Assad has no reason right now to sit down and negotiate for peace because he sees himself winning militarily on the ground."

The latest statements from Washington hint at the possibility of expanded US involvement, but these could well be bluster aimed at gauging the resolve of the Assad administration and its principal allies, Russia and Iran.

Also, while it is believed that the CIA has been running a covert training programme for Syrian rebels in neighbouring Jordan for some time - claims denied by Amman - the reality is that US military assistance of the magnitude that could make a perceptible difference on the battlefield is, as of today, the stuff of rebel fantasies.

In footage aired by Al Jazeera this week, an FSA fighter operating in an open battlefield on the outskirts of Aleppo says: "We need heavy weapons. All we have are Kalashnikovs… We have RPGs [rocket-propelled grenades], but we need things like anti-tank missiles."

Yet it is unlikely, according to several US defence analysts, that the FSA will get the anti-aircraft surface-to-air missiles and anti-tank weapons that it wants from the US and the Friends of Syria group.

"I think the best way Washington can ensure that these higher-end weapons won't fall into the wrong hands is by not providing these weapons, which unfortunately is exactly what the FSA needs," Kimmitt told Al Jazeera.

Death and displacement

The likely downside of limited US military assistance to the FSA is that it will end up making a bad situation worse, increasing violence levels and adding to the body count in a war that seems to have all the trappings of a sectarian blood feud.

The latest UN report says the Syrian conflict, which began in 2011 as part of the so-called Arab Awakening, has claimed the lives of more than 93,000 people so far, with the monthly toll averaging 5,000 over the past year.

More than 6,500 children are believed to have died across the country as a result of the fighting, which has also displaced 2.5 million civilians, forcing them to take shelter in crowded camps in neighbouring countries or within Syria itself.

For all the savage killings and human-rights abuses, what forced the Obama administration's hand by most accounts was the involvement of Shia Hezbollah fighters in winning the battle of Qusayr for the Assad administration, which draws its support mainly from Syria's Alawites, a Shia offshoot.

With an emboldened Assad threatening to retake the northern province of Aleppo and the central provinces of Homs and Hama from rebel control, there was a sobering realisation among US, European and Sunni Arab leaders that the battlefield equation was shifting quickly in favour of the Syrian leader and his regional backers.

"The whole region is about to blow up," Lindsey Graham, the Republican senator and ally of no-fly zone advocate John McCain, said on NBC's Meet the Press programme, referring to the potential effects of Syria's instability on Jordan, Egypt and Israel.

"And our foreign policy to me - I don't understand it. Whatever it is, is not working."

Fear of 'blowback'

In all fairness, the Obama administration has good reason to be wary of an Afghanistan-style "blowback" given the Islamist orientation of many of the Syrian opposition groups, which are backed financially and militarily at present by Saudi Arabia and Qatar.

Some of the groups in the frontline of the anti-Assad armed campaign, the Jabhat al-Nusra for example, are not shy about their affiliation with al-Qaeda, making them unlikely bedfellows of the US-led bloc backing the Syrian opposition.

Given the bitter outcomes in Iraq and Libya, where Western "liberal intervention" has left the countries in a state of political instability and security vacuum, no US administration - especially one led by a Democrat who had opposed the Iraq war and promised to engage Washington's friends and foes alike - could have been expected to rush into the Syrian conflict in its early stages.

But three years on, the choice President Obama faces is a far more vexing one: between meekly accepting a resurgent, Iranian- and Russian-backed Middle East leader accused of using the nerve gas sarin on his own people, and bolstering the FSA, a loose umbrella group of rebel factions that has been playing second fiddle to the Syrian Islamist Front, which comprises arguably the most effective fighting force, the Ahrar al-Sham.

As Kimmitt, the former US State Department official, described it: "The world community, with the exception of countries such as Iran and Russia, want to see Assad gone… What you have is a very reluctant American administration which is not seeking intervention or involvement, but feels morally bound to support the people of Syria, and as a result is supplying the arms."

Friends in need

Compared with the West's hesitant embrace of Syria's opposition, Iran and Russia have spared no effort or expense to stand by their long-standing strategic ally

The Islamic republic has backed Assad with military hardware, technical and personnel support, intelligence, oil and, not least, the services of its Hezbollah and Iraqi Shia militia proxies.

"A decision has already been taken in Tehran to furnish Bashar al-Assad's forces with several thousand, initially 4,000, Revolutionary Guards. [So far] there has been some intelligence officers but not an actual contingent," said Robert Fisk, the Middle East correspondent of Britain's Independent newspaper, in an interview with Al Jazeera last week.

Iran has denied the report but, then again, it has used the tactic of "plausible deniability" to conceal its assistance to Assad since the outset of the Syrian uprising.

Russia, on the other hand, is more transparently keen to see Assad remain in power. It has acknowledged signing an agreement last month to sell Syria S-300 air-defence missiles, which are considered to be the most powerful in aircraft-interception technology.

Introduction of such advanced air-defence systems to Syria's war arsenal could prove to be a game-changer by greatly raising Israel's threat perception and making any US-enforced no-fly zone very costly.

Before travelling to the G8 summit in Northern Ireland where he discussed the Syrian crisis with Russian President Vladimir Putin, Obama told Charlie Rose of PBS: "We're not taking sides in a religious war between Shia and Sunni. Really, what we're trying to do is take sides against extremists of all sorts… in favour of, over the long-term, stability and prosperity for the people of Syria."

The trouble is, the Russians and the Iranians insist they have the same lofty objectives. And no price in Syrian blood and tears, it seems, is too high to achieve the rival camps' ostensibly common goals.

Follow Arnab Sengupta on Twitter: @arnabnsg