The collapse of Syria's Assad regime - with President Bashar al-Assad not even informing his closest associates before fleeing to Moscow - has left regional and international players scrambling to stabilize the country.

Of course, there have been numerous attempts to restore stability to Syria ever since the start of its civil war in 2011, after Assad brutally repressed peaceful Arab Spring demonstrations. Despite the many failures, United Nations Security Council Resolution 2254, adopted unanimously in December 2015, remains the cornerstone of international diplomatic efforts to resolve the Syrian conflict. It provides a clear roadmap for a Syrian-led political transition under a new constitution, with UN-supervised elections and measures to ensure inclusive governance.

True, there has been little progress on any of these fronts. The Constitutional Committee, the body charged with implementing Resolution 2254, exemplifies both the potential and the limitations of the UN process. Comprising representatives of the Assad regime, the opposition, and civil society, it was supposed to draft a new constitution that could serve as the foundation for a political settlement. But the committee has achieved little of substance after numerous rounds of meetings in Geneva, owing to obstruction by the regime's delegation.

The regime faced no consequences for derailing the process, because the UN Security Council itself was deeply divided. Russia's status as a permanent, veto-wielding member allowed it to shield Assad from more forceful international action, and its 2015 military intervention saved his regime and fundamentally altered the balance of power on the ground. While UN Special Envoy Geir Pedersen tried to break the impasse by enticing the regime with the prospect of sanctions relief, such proposals had no effect.

Now, suddenly, everything is different. While the first foreign dignitary to travel to Damascus after the fall of the regime was Turkish intelligence chief Ibrahim Kalin, the second (from what we know) was Pedersen. Moreover, many governments say they are in contact with the lead rebel group, Hayat Tahrir al-Sham (HTS), and its interim government. The fact that the United States, the United Kingdom, and others still officially designate HTS as a terrorist organization has not been an issue.

Although much is up in the air, the 2015 UN roadmap remains the best option for ensuring inclusive governance, which is a precondition for stability in Syria. The question, however, is whether all domestic and regional players will go along with the process.

Israel has not hesitated to advance its forces beyond the Golan Heights, throwing out an arrangement that had prevailed since the 1973 Yom Kippur War (when even the minimal gains that it made in the area inflamed passions across the Arab world). It has also been carrying out preemptive air strikes against what is left of Syria's military hardware and weapons facilities.

For Turkey, the biggest question is whether it can accept a Syrian governance framework that includes the Kurds. The Turkish government's priority is to marginalize any elements associated with the Kurdistan Workers' Party (PKK), which it regards as a terrorist group (as do the US and the European Union). Ideally, a new settlement in Syria could even help to defuse the Kurdish issue in Turkey itself.

One obvious risk is that remnants of the Islamic State (ISIS) will exploit the new uncertainty to strengthen their own position. But both HTS and various Kurdish groups have fought ISIS for years, and they will now be even more determined to resist it. A key strength of the UN process is the absence of favorable alternatives; were it to collapse, the outcome would be catastrophic for all concerned. The victorious rebels' focus on building and maintaining state institutions shows that they are well aware of the dangers.

To succeed, the process must be carried out by Syrians for Syrians, but with external assistance. The humanitarian situation is dreadful and requires immediate attention. The EU and the US should make it clear to all relevant actors that they are ready to lift the economic sanctions on Syria in support of a political transition.

The stakes are especially high for Europe, whose politics are still haunted by the 2015 refugee crisis. Repeating that episode would be a nightmare. And Turkey, of course, has a vital interest in stability on its border. It has long hosted millions of Syrian refugees whom it would love to return home, and many are now expressing a readiness to go.

The process that lies ahead will be long and complicated, though. Syrian governance has never been a simple affair. If any of the key players starts pursuing their own agenda unilaterally, conditions could deteriorate rapidly. Nonetheless, the UN process represents the best way forward, giving the organization a chance to show the world that it remains indispensable for situations such as these.

From Project Syndicate