Washington has suspended nonlethal aid to Syrian rebels after Islamist militants seized warehouses containing U.S.-provided supplies close to the Turkish border, U.S. officials announced Wednesday. General Salim Idris, commander of the Free Syrian Army, the non-Islamist rebel group that the United States has weakly supported, was forced to flee Syria after his headquarters was occupied by the same Islamist militant group.

The militants belong to the Islamic Front, an umbrella group formed last month by seven Islamist militias. Many of these groups, some of the largest rebel factions outside al-Qaeda, had previously cooperated on the battlefield with the Free Syrian Army, and some of the groups had defected from it.

They may have been motivated to join the Islamic Front by the prospect of greater foreign support, particularly from Saudi Arabia, which has been more assertive in Syria after bitter disagreements with the Obama Administration’s vacillating Syria policy.

Syria’s rebels have been disappointed by the low level of support from the United States and other western countries. Young men increasingly have gravitated toward Islamist groups, which generally are better armed, more lavishly equipped, and well-funded by Saudi Arabia, Qatar, and other Arab oil kingdoms.

Two al-Qaeda factions, the al-Nusra Front and the Islamic State of Iraq and Syria, also have flourished inside Syria and clashed with both the Free Syrian Army and members of the Islamic Front.

The formation of the Islamic Front and its seizure of Free Syrian Army supplies and bases reflects growing infighting and polarization within the broad rebel coalition. Islamists also have escalated their intimidation of Syrian civilians and non-Islamist political leaders.

Islamist factions also have kidnapped and threatened western reporters in Syria, prompting 13 international news organizations to write an open letter this week that warned that such behavior threatened the coverage of the Syrian conflict.

The rising power of Syrian Islamists is not only a threat to Syria’s people but an ominous outcome of the Obama Administration’s collapsing Syria policy.

The Administration has lagged far behind the curve from the beginning of the Syrian rebellion. It initially failed to recognize the nature of Syrian President Bashar al-Assad’s regime, was slow to call for Assad to step down, was slow and ineffective in taking actions to force Assad out of power, and announced a “red line” against the use of chemical weapons without giving adequate attention to how it would enforce the line, if challenged.

After Assad violated the Administration’s chemical “red line,” the White House belatedly agreed to provide arms to the Syrian rebels. This was too little too late.

Moreover, the Administration made a bad situation worse by proclaiming it would launch military reprisals against the Assad regime before eventually acceding to a Russian-engineered diplomatic agreement to disarm Syria’s chemical weapons. This bolstered Assad, strengthened Russian influence, undermined America’s reputation as a reliable ally, and demoralized the non-Islamist Syrian rebels.

The bottom line is that the Obama Administration’s vacillating Syria policy has left America increasingly irrelevant in shaping the outcome of the intensifying Syrian civil war.