Members of the Free Syrian Army. Photo: World Defence News.

The Obama administration has modified its approach to the conflict in Syria in recent weeks, according to the Wall Street Journal, which reports “they don’t want an outright rebel military victory right now because they believe, in the words of one senior official, that the ‘good guys’ may not come out on top.”

The change has been precipitated by al Qaeda’s emboldened maneuvers in the country. A top al Qaeda figure from Pakistan recently traveled to Syria and al Qaeda in Iraq, the network’s branch in Iraq, announced it was merging with the Nusra Front in Syria.

According to the Journal, officials fear that the increasing Islamist influence means a victory would undercut hopes for finding a diplomatic solution. It would also shatter national institutions along with what remains of civil order, increasing the danger that Syrian chemical weapons will be used or transferred to terrorists.

The White House has drawn up elaborate plans for a post-Assad Syria that includes an orderly political transition that keeps the country together and preserves Western interests, administration officials tell the Journal.

The U.S. fears the plans could be jeopardized if rebels overrun key institutions such as “unit 450,” the Syrian military branch that U.S. officials say oversees Syria’s chemical-weapons stockpile.

The administration goal, according to people briefed on the effort, is to provide enough aid to strengthen U.S.-vetted fighters without tipping the balance so far that Islamists who dominate rebel ranks will be able to overrun the regime and its institutions.

“We all want Assad to fall tomorrow, but a wholesale institutional turnover overnight doesn’t make a whole lot of sense,” a senior U.S. official said. “The end game requires a very careful calibration that doesn’t tip the meter in an unintended way toward groups that could produce the kind of post-Assad Syria that we aren’t looking for.”