Iran and Russia may find a way to push past their strategic differences and make the ceasefire work, but it will be much more difficult to forge agreements on Syria's other intractable issues at the upcoming peace conference.

In mid-December, after a final military assault on Aleppo alongside Syrian regime forces, Russia announced that the city was free of rebels. A week later, Moscow and Turkey signed a ceasefire agreement. The Kremlin seems eager to ring in Donald Trump's presidency with a renewed effort to find a political solution and end the war, beginning with peace talks scheduled to be held in Astana, Kazakhstan, at the end of January.

Yet the ceasefire is under threat only days after it began, with Hezbollah and Assad regime forces fighting rebels in the Damascus suburbs of Wadi Barada and East Ghouta. Ten rebel factions have already threatened to boycott the Astana talks unless the ceasefire is fully implemented.

Wadi Barada has been under siege since July, when Syrian and Hezbollah troops cut access routes to a spring that provides much of the capital's water. Under the direction of its Iranian patron, Hezbollah has been working diligently to strengthen its control over the suburbs, in line with a wider plan to establish a Sunni-free corridor linking Iran to Lebanon via Iraq and Syria. This entails securing Damascus as the Alawite capital, with Bashar al-Assad staying on as president. The group aims to finalize this corridor before negotiating any division of power in Syria, so it is sidestepping the ceasefire as much as possible.

For its part, Russia genuinely seems to want the ceasefire to work, at least until the Astana meeting. Yet Iran is not trying so hard, indicating that Moscow and Tehran have different priorities in Syria. Iran's involvement in the lead-up to the agreement was limited -- while it sent a delegation to the final meeting in Moscow, the ceasefire itself was brokered by Russia and Turkey.

This does not mean that Iran and its Shiite militias will be pushed out of Syria anytime soon, however. The stakes are too high for that to happen, and all of the pro-Assad players still need each other. Yet even if the regime and the rebels push past the limited ceasefire violations -- which seems likely given the generally strong appetite for a political solution -- Hezbollah's actions signal potential disagreements between Russia and Iran regarding the future of Syria. Moscow prefers a political solution that guarantees Russia's sway over Syria's state institutions, in which it has invested for years. Yet Iran and its proxies prefer a military solution that yields faster demographic changes, with the aim of consolidating the "Shiite crescent" they have been working on for decades.

DISPARATE INTERESTS

Iran and Russia's alliance in Syria has always seemed like a temporary one -- while they agree on war, they differ on peace. Tehran often treats Assad's army as just another one of its militias in Syria, and a weaker one at that. It does not trust the army to secure its "Shiite corridor," instead relying on Hezbollah and other Shiite militias to help change the demography of towns within regime-held areas. Iran's Islamic Revolutionary Guard Corps (IRGC), which oversees much of the pro-Assad camp's military activity, believes that any future solution in Syria will be based on sectarian grounds. Accordingly, Tehran prefers a partition plan that guarantees a Shiite statelet under its control. It also wants to make Damascus a full client government with weak institutions that are incapable of making independent decisions, similar to what it has in Lebanon. Among other things, this would give Iran access to Israel's northern borders via the Golan Heights, expanding its current access through Hezbollah-controlled southern Lebanon.

In contrast, Russia has no interest in demographic changes or sectarian division in Syria. Vladimir Putin does not want Assad's authority to be usurped behind the scenes by IRGC-Qods Force commander Qasem Soleimani. Instead, he prefers a political solution that leads to a gradual transition of power. Syria's state institutions are more significant to Russia than Assad and his family are. Brokering a solution would give Putin a chance to secure his influence over these institutions, and perhaps even strengthen his negotiating position with Europe on a variety of other interests.

These differences between Russia and Iran are hardly irreconcilable. Putin does not mind an Iranian corridor in Syria as long as Tehran does not try to overpower Russia in Damascus. And Iran knows that it needs Moscow given that the incoming Trump administration has signaled a tougher U.S. stance on the nuclear deal and other Iranian interests. So if Russia wants to call the shots while Iran secures its position in eastern Syria, Tehran will not make too much noise -- at least for now.

STUMBLING BLOCKS

Iran's main worry about the ceasefire is Turkey's preeminent role. Moscow needs Ankara to help win over the Sunni opposition and Sunni street in Syria, while Turkey needs Russia to help protect its borders against Kurdish forces. Yet Turkey and Iran are still not in agreement. Although Ankara seems to have given up its past insistence on ousting Assad, it still has issues with Iran's proxies.

Shortly after the ceasefire was announced, Turkish foreign minister Mevlut Cavusoglu declared to reporters back home, "All foreign fighters need to leave Syria. Hezbollah needs to return to Lebanon." He also stated that Turkey would guarantee rebel compliance with the ceasefire, Russia would guarantee Assad's adherence, and Iran would help monitor regime forces and allied Shiite militias.

Hezbollah responded the next day with a series of statements. Political Bureau chief Ibrahim Amin Assayed declared that the group will not leave Syria with or without an agreement. Similarly, a militia commander told Lebanese media that Hezbollah is in Syria to fight terrorism, and that the war on terrorism is not over. He added that the group entered Syria after reaching an agreement with the Syrian government, and only a similar agreement will get them out. As for the ceasefire violations in Wadi Barada, he blamed the opposition.

Likewise, Ali Akbar Velayati, a close advisor to Iranian Supreme Leader Ali Khamenei, issued a statement on January 3 insisting that Hezbollah will remain in Syria even after the ceasefire. Two days later, the Russian ambassador in Beirut told Lebanese media outlet al-Modon that Moscow will not ask the group to leave Syria because they are partners in fighting terrorism.

In short, Turkey is the only party calling on Hezbollah to withdraw -- a fact that will not sit well with Iran. Although Ankara understands the current military need for Shiite militias in Syria, it still wants some sign or guarantee that they will eventually leave. Russia must also find a way to bring Saudi Arabia and Qatar along. These longstanding Sunni supporters of the rebellion will not be easily swayed as long as Assad is still acknowledged as Syria's president, and they are even more concerned about Iran's attempts to cement a Shiite crescent in the region.

Another stumbling block is Russia's unilateral deals with opposition fighters in certain areas, especially around Damascus. These deals guarantee that fighters can remain in their towns if they respect the ceasefire, but Iran wants all Sunnis out of such areas for demographic reasons, and it will have even more capacity to realize that goal now that Shiite forces have been freed up by the victory in Aleppo. So why did Russia make these deals knowing that Iran will try to break them? Moscow probably hoped to save face with the Syrian opposition and the Sunni majority population. As mentioned previously, Turkey might be able to help with that depending on the reaction from Saudi Arabia and Qatar, which is still vague.

BEYOND THE CEASEFIRE

Although Iran and Russia might find a way around their differences for the time being, a host of longer-term challenges looms on the horizon. Assad's fate has not been determined, and any political solution will require all of the parties at Astana to forge understandings on that and many other problematic issues, including the presence of Shiite militias and the question of who will reconstruct Syria so that refugees can return. Moreover, the relevant Gulf powers have not been invited to the conference, so it is unclear how they will respond to any decisions reached there. Barring their inclusion in the process or some other form of guarantee on Assad's fate and Shiite militias, the Astana initiative will have little chance of success, and all other problems will stay on hold.

For its part, the United States has been absent from the entire ceasefire process and did not have any significant feedback when the agreement was announced. Yet the Trump administration will take office before the Astana meeting, and while the timing is very tight, there might still be a place at the negotiating table for U.S. officials if they want it.

Hanin Ghaddar, a veteran Lebanese journalist and researcher, is the Friedmann Visiting Fellow at The Washington Institute.