The Russian-American plan to eliminate Syria’s chemical weapons — now embodied in the United Nations Security Council Resolution 2118 — may open a more constructive approach to ending the country’s civil war, because the Security Council is also demanding that the long-planned Geneva II conference on Syria convene as soon as possible.

Rightly so. Elimination of Syria’s chemical-weapons stockpiles and a political process to end the war must occur simultaneously.

As a practical matter, efforts to verify, secure and eventually destroy Syria’s huge supply of chemical weapons cannot be implemented without a lasting ceasefire. But synchronizing the two processes is necessary for other reasons, too.

Aside from the human suffering caused by Syria’s war, we should be aware of the potentially dire regional consequences.

Some people now warn of a “Lebanonization” of Syria — the partition of the country into rival fiefdoms and quasi-independent regions. Syria’s fragmentation is not the only plausible scenario.

Indeed, the Lebanon metaphor is too benign. Unlike with Lebanon during its 15-year civil war, no regional power today would be able to contain Syria’s war within its borders. As a result, it is much more likely that Syria’s disintegration would call the entire post-World War I Middle Eastern state system — also called the “Sykes-Picot” system — into question.

Such regionwide instability is not just a theoretical scenario; it follows from developments on the ground. Lebanon’s established political contours already are beginning to blur under the relentless pressure of the Syrian conflict.

A zone of de facto control by Lebanon’s Hezbollah and Syrian regime forces has emerged between Baalbek and Homs, straddling the Lebanese-Syrian border.

Likewise, the fighting has created highly fluid conditions in the Kurdish-majority areas of Iraq and Syria. Since the fall of Saddam Hussein, the Kurdistan Regional Government (KRG) in northern Iraq has effectively established de facto autonomy vis-a-vis the central government in Baghdad. Regional and domestic developments could push the Kurdish authorities in Erbil, their capital, toward declaring formal independence.

With its oil income and good neighborly relations with Turkey, such a state would be viable. Indeed, the KRG government has long made clear that it respects Turkish sovereignty and will not interfere with relations between Turkey’s government and its own Kurdish population.

And, if only for its own security, the KRG is attempting to extend its power, formally or informally, into northern Syria.

Regional acceptance of a Kurdish state-building project that transcends today’s KRG-controlled borders would depend, among other things, on the scale of the Kurds’ national ambitions. From Turkey’s perspective, a confederation of Syria’s northeastern region with the KRG might be favorable to continuing domestic Kurdish unrest, much less rule, by the anti-Turkish Kurdish Workers Party (PKK) along its border with Syria.

In contrast, any attempt by the KRG to establish a Kurdish corridor to the Mediterranean would certainly meet resistance, not only from Turkey, but also from other warring factions in Syria.

What, however, would Kurdish independence mean for the rest of Iraq?

This is not only a question of territory, borders, and oil, but also one that concerns the domestic balance of power.

With a Kurdish exit removing the third constituent element — besides Shiite and Sunni Arabs — of Iraqi politics, the country’s sectarian polarization would most likely deepen.

Moreover, Kurdish independence could encourage demands for autonomy in the Sunni-majority provinces bordering Syria, Jordan and Saudi Arabia — a third region where Syria’s civil war is blurring international borders.

Social, tribal and economic ties between the provinces of Deir al-Zour in Syria and Anbar in Iraq are strong and have strengthened further as control by the Syrian and Iraqi governments has loosened.

It is astonishing how many regional observers seem to expect, hope or fear that such developments will somehow lead, almost automatically, to a “new Sykes-Picot” — to the establishment of a new regional order in the Middle East created by today’s great powers.

Such expectations are patently unrealistic. Europeans and Americans have learned — and China, Russia, and others have learned from Western experience — that external powers cannot successfully engineer political arrangements or regional order in the Middle East.

Rather than pondering or devising new borders, regional and external powers need to focus their efforts on holding Syria together. The planned Geneva II conference is a necessary first step.

To be sure, there are many reasons to be pessimistic about the willingness of Syria’s warring parties to engage in serious negotiations. Indeed, no one — not Russia, the United States, Iran, Saudi Arabia or other external patrons of either the regime or the opposition — can guarantee that Geneva II will succeed.

But all of them could improve conditions for negotiations by sending the same message to their respective Syrian clients, namely that they henceforth exclude a military victory by one side over the other.

Thus Russia and Iran will have to tell Syrian President Bashar Assad that they will not support his effort to seek a military victory. Saudi Arabia, the U.S., Turkey and others will have to tell the National Coalition for Syrian Revolutionary and Opposition Forces that it will not win on the battlefield; the Salafists must hear this message from Saudi Arabia, too.

And Turkey and Qatar, for their part, will have to pass the same message to the Muslim Brotherhood.

The message to all of these groups should be consistent: We will continue to support you politically, financially and in negotiations with the Syrian regime, but we will no longer support a military solution.

This would be a strong incentive to go to Geneva. Warring parties start to negotiate seriously only if and when they know that other alternatives are out of reach.

Volker Perthes is chairman and director of Stiftung Wissenschaft und Politik, the German Institute for International and Security Affairs, Berlin. © 2013 Project Syndicate (www.project-syndicate.org)