A fighter from the Islamist Syrian rebel group Jabhat al-Nusra poses at a checkpoint in Aleppo in 2013. (Molhem Barakat/Reuters)

As the U.S.-led coalition has begun to gain ground against the Islamic State in Syria, officials have begun focusing attention on another jihadist group they fear may pose a more dangerous long-run threat there, the al-Qaeda affiliate known as Jabhat al-Nusra.

Jabhat al-Nusra has played a clever waiting game over the past four years, embedding itself with more moderate opposition factions and championing Sunni resistance to Syrian President Bashar al-Assad. The group has mostly avoided foreign terrorist operations and has largely escaped targeting by U.S. forces. Meanwhile, it has developed close links with rebel organizations such as Ahrar al-Sham that are backed by Turkey, Qatar and Saudi Arabia.

But the global jihadist ambitions of Osama bin Laden remain part of Jabhat al-Nusra’s DNA. U.S. officials report increasing evidence that the group is plotting external operations against Europe and the United States. Its operatives are said to have tried recently to infiltrate Syrian refugee communities in Europe.

A stark warning of the danger ahead comes from the Institute for the Study of War, which closely follows events in Syria. In a forthcoming forecast, the institute argues that by January 2017, “Jabhat al-Nusra will have created an Islamic emirate in northwestern Syria in all but name” and will merge with the supposedly more moderate Ahrar al-Sham.

“The merger, even if incomplete, will accomplish a major Jabhat al-Nusra objective to unify the northern Syria opposition under its own leadership. . . . It will lay the groundwork for Jabhat al-Nusra to absorb or defeat remaining independent elements of the opposition.”

The agonizing question for the Obama administration is how to combat Jabhat al-Nusra as it moves to fill the vacuum left by an Islamic State that is losing territory and popularity. As with most other aspects of the Syrian war, the administration finds nothing but bad choices. The current version of this policy nightmare is whether to ally with Russia in suppressing the Jabhat al-Nusra threat.

Secretary of State John F. Kerry appears to be attempting a tricky three-cushion shot: Kerry’s plan would include joint U.S.-Russian operations against the group, as well as the Islamic State. Kerry also hopes to reduce Assad’s attacks on moderate rebel forces so that they (rather than Jabhat al-Nusra) can gain ground in a post-Islamic State Syria.

Like many of Kerry’s gambits, this is a high-risk maneuver. Even his supporters fear that it’s born more out of desperation than a carefully articulated strategy.

According to one source familiar with Kerry’s plan, it would begin with an attempt to reduce violence, as happened after the initial Russian-American “cessation of hostilities” plan was announced in February. If violence ebbed, and the Assad regime allowed humanitarian assistance to reach besieged areas in Aleppo and elsewhere, then the United States would begin sharing targeting information with Russia.

One sweetener in this still-untested deal is that the Assad regime would agree to a “significant reduction” in its air operations over rebel-held areas. If this curb on Assad’s barrel-bombing tactics succeeded, it could begin a real path toward de-escalation. But even administration officials who have helped frame the Russia-America package are skeptical that the details will fall into place.

Bassam Barabandi, a senior adviser to the opposition coalition, says that most Syrians recognize that Jabhat al-Nusra is a terrorist group and will support gradual U.S. efforts to combat it. But he cautions that Syrians fear the U.S.-Russia pact will only strengthen Assad and “kill the revolution” against Assad’s regime.

Kerry’s diplomacy suffers from a weak U.S. bargaining position. Russia and Syria think they’re winning, as they tighten their siege of Aleppo and other rebel strongholds. There’s little incentive for them to make the serious concessions that might bring buy-in from the opposition. The United States, by contrast, has failed in a three-year, CIA-led effort to build a moderate opposition force that could draw rebels away from Jabhat al-Nusra and its Sunni allies.

The U.S. military has had more success fighting the Islamic State in eastern Syria with a largely Kurdish force known as the YPG. But this Kurdish-centric strategy antagonizes both Turkey and the official Sunni-led opposition.

Five years on, the Syrian civil war remains a problem from hell. Allying with Russia against Jabhat al-Nusra risks deepening the terrorist group’s support within Syria and further alienating Sunnis; but continuing with the current strategy is almost certain to fail.

The right approach now, as when this mess started, is for the United States to aggressively, passionately, visibly provide humanitarian aid, governance and security assistance in areas that are liberated from Assad and the jihadists. “Realism” can be a trap in Syria; doing the right thing is also good policy.

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