The Geneva II conference on Syria, set to begin in Montreux, Switzerland, this week, is unlikely to achieve its goal of forming a transitional governing authority with full executive powers. But what it can do is launch a much-needed political process and, more important, produce a ceasefire agreement between government and opposition forces. Only when the fighting has stopped can Syria make genuine progress toward a political transition.

Of course, al-Qaida-linked jihadist groups like the Islamic State of Iraq and Syria (ISIS), which has become a potent force on the ground, and the Nusra Front will not and should not be represented in Montreux — not least because they will not feel bound by any agreement.

But this should not serve as an excuse not to pursue a ceasefire. After all, even stopping the fighting between regime forces and some armed groups — that is, those that associate themselves with the Syrian National Coalition, or are at least willing to coordinate with the Free Syrian Army (FSA) and the partly Saudi-sponsored Islamic Front — would be a major achievement.

A ceasefire is critical, because the fighting serves the interests of the most brutal elements on both sides of the conflict. This includes the core leadership of President Bashar Assad’s regime, which is now supported by Hezbollah and Iraqi militias, as much as the ISIS, which is composed largely of non-Syrian fighters who are unconcerned about rebuilding the country or safeguarding its people’s future.

As in any civil war, such entrepreneurs of violence become increasingly likely to carry the day the longer the conflict endures. They feed on their own atrocities or on those of their opponents to win support through fear rather than conviction — using videos to raise funds and recruit members.

With skilled fighters and plenty of money and arms, the ISIS and the Nusra Front thrive amid persistent war and anarchy. Meanwhile, the Assad regime benefits from the fact that parts of the country that it no longer controls cannot be called “liberated zones,” given the prevailing chaos and extremism in these areas.

A ceasefire would initiate a shift in this dynamic, allowing humanitarian supplies to reach the areas where they are needed most urgently, while halting the country’s gradual “Somalization.” This would help to stem the flow of refugees — and the spillover of violence — to neighboring countries, particularly Lebanon and Iraq.

Furthermore, if the ceasefire held, it would facilitate economic reconstruction, while enabling moderate political actors and civil society to win back some power from the extremists — a shift that ordinary Syrians would welcome.

Indeed, people in jihadist-controlled areas are deeply unhappy with al-Qaida thugs terrorizing them and trying to enforce their version of Islamic mores — so much so that the Assad regime increasingly appears to be a better alternative to continued warfare or an al- Qaida takeover.

The problem is that, as long as violence prevents moderate forces from restoring local services and administrative structures, people’s capacity for resistance will remain weak. International organizations could treat such structures as de facto authorities, supplying them directly with aid and also giving nongovernment organizations or United Nations investigators an opportunity to collect evidence of war crimes for future judicial or truth-commission proceedings.

To be sure, fears that a ceasefire could lead to a stabilization of the conflict’s front lines, turning them into semi-permanent lines of division, are not without merit.

After all, a ceasefire is not a peace agreement; it would, for the time being, leave regime and opposition forces in their respective positions. But having different authorities administer different parts of Syria is preferable to the absence of any responsible governance across large swaths of the country.

Moreover, a ceasefire would enable the FSA and its allies to coordinate action with units of the regular army against al-Qaida bands, which would undoubtedly try to sustain the violence. Even such limited cooperation would advance the “Geneva process” — especially negotiations aimed at establishing a transitional authority that would command the armed forces.

Given that the Assad regime has overwhelming firepower, its consent is vital to achieving a ceasefire agreement. Responsibility for convincing Assad to stop bombing and shelling opposition-held areas would fall primarily on his international allies, Russia and Iran.

In doing so, they should bear in mind that it was Assad who led the country into civil war by choosing a military solution when high-level members of his own government and political party argued for a negotiated settlement.

Neither Russia nor Iran has an interest in prolonging a war that is destabilizing the Middle East and fostering the spread of al- Qaida-style extremism. Indeed, both have already helped to bring the Syrian regime to Geneva. Now, they must make their support for Assad’s delegation conditional upon his acceptance of a ceasefire. Otherwise, prospects for an outcome that leaves Syria intact and viable will only become bleaker.

Volker Perthes is director of Stiftung Wissenschaft und Politik at the German Institute for International and Security Affairs in Berlin. © 2014 Project Syndicate (www.project-syndicate.org)