It’s make or break time for U.S. diplomacy in Syria: weeks of legwork, dozens of phone calls exchanged between Washington and Moscow and a marathon session of closed-door negotiations on February 22 produced a joint product codifying yet another cessation of hostilities agreement.

The principles of the international community’s latest attempt at a temporary cease-fire are well known to anyone who has been following the conflict since its inception. Hostilities between the Assad regime and opposition forces are to stop by midnight on February 27. Rebel groups who wish to partake in the cease-fire are required to let the United States or Russia know twelve hours before the fighting is scheduled to stop. Washington and Moscow will establish a mechanism to monitor the cease-fire and ensure that there is some level of transparency on violations. And the International Syria Support Group (ISSG) will form a task force, in part to generate a communication flow among all parties to the conflict. Last but not least, the U.S.-Russia deal excludes the Islamic State and Jabhat al-Nusra from the cease-fire—offensive military actions against both groups are perfectly legitimate under the agreement.

At its core, the February 22 de-escalation accord is the third attempt by members of the ISSG to tamp down the violence in Syria. UN Security Council Resolution 2254 and the original cessation of hostilities agreement drafted on February 11 were either quickly violated by the Assad regime or ignored by the Russians—knowing full well that the Security Council and the ISSG would be unable to exact repercussions. Secretary of State John Kerry and his foreign ministerial colleagues are hoping beyond all hope that this latest truce will do what the previous two did not: cease the killing enough to allow humanitarian aid into dozens of besieged Syrian cities, and jolt a dormant peace process out of its coma.

There is a small degree of hope that this may transpire. Russian President Vladimir Putin, the man who has devoted dozens of fighter jets and at least four thousand of his soldiers to Assad’s defense, is at the very least making calls around the world in order to make sure the key players understand precisely what is in the truce. On February 24, Putin made calls to Israeli Prime Minister Benjamin Netanyahu, Iranian President Hassan Rouhani and Saudi King Salman, all the while receiving a commitment form Bashar al-Assad that he would indeed respect the cease-fire. The Syrian opposition’s High Negotiations Committee confirmed on the same day that they, too, would follow the agreement, to test whether the Syrian regime and Russia were in fact committed to its implementation.

These developments are positive, but they are no guarantee. In fact, there is an exponentially greater chance that the U.S.-Russia cessation of hostilities agreement will fail the minute it takes effect. The United States understands how difficult it will be for Assad and the moderate opposition to stop firing at one another, as is evident in President Barack Obama and Secretary Kerry’s own remarks.

Assuming that Moscow genuinely wants this agreement to succeed, what can Washington do to make it more likely that hostilities will actually cease by midnight this Saturday? The bottom line: get Russian diplomats in a room, keep them there and try to plug the gaping holes that are currently embedded in the truce.

The fact that the ISSG cease-fire task force will meet for the first time only twenty-four hours before the truce is set to take effect is a terrible omen. Secretary Kerry and Foreign Minister Sergei Lavrov cannot waste anymore time, because the unanswered questions that will complicate implementation of the cease-fire are nearly endless. If you’re looking for a metaphor for the ISSG cessation of hostilities, think of a leaky fishing boat in the middle of the ocean.

Without any third-party or neutral U.N. observers on the ground to monitor the truce, how can the ISSG separate fake violations that the parties may report to embarrass or delegitimize their enemies from real ones? Will accountability for breaches on both sides serve as a real deterrent to the fighters on the ground, or is this simply a naming-and-shaming exercise? Will the United States and Russia be able to arrive at a consensus on how to punish Assad, or the various rebel groups, in the event of a violation, particularly at a time when both nations remain far apart regarding some fundamental aspects of the conflict (the status of Assad in a transitional government, the status of Assad as the end of a transitional government, which rebel groups are actually terrorists and which are moderates, and so on)?

None of these questions have been answered to date. Indeed, it’s not at all clear if any have even been broached given the inability of the cease-fire task force to meet. One hopes that Kerry and Lavrov discussed some of these issues during the past week on a bilateral basis, because without an understanding of how the truce is supposed to work, it will only be a matter of time before the international community is coerced back into a corner, looking at themselves in the mirror and wondering what possibly went wrong.

The “Plan B” option that John Kerry disclosed to Congress may be closer than we think.

Daniel R. DePetris is an analyst at Wikistrat, Inc., a geostrategic consulting firm and a freelance researcher. He has also written for CNN.com, Small Wars Journal and the Diplomat.

Image: Flickr/Christiaan Triebert