The CIA has been expanding a covert program to train US-backed opposition fighters in Syria, The Washington Post on Thursday cited US officials as saying.According to the report, the agency was expected to train only “a few hundred” moderate fighters each month following the expansion of the program. The official told the Post that the limited number of CIA-trained fighters would not be enough to overcome Islamic extremist rebels who are also fighting against Syrian President Bashar Assad’s regime.The limited impact of the clandestine program allows the CIA to provide enough backing to the moderates to ensure they don’t lose in the civil war, but not enough for them to hail an overall victory, the Post cited the officials as saying.Crisis in Syria - full JPost.com coverageFewer than 1,000 opposition fighters received training from the agency this year, the report cited current and former US official as saying.Meanwhile, Assad allies Iran and its proxy Hezbollah have reportedly trained more than 20,000 guerrillas to fight for pro-government forces, the Post cited US intelligence analysts as estimating.In June, the Los Angeles Times reported that CIA operatives and American special-operations units have been training Free Syrian Army soldiers with anti-tank and anti-aircraft weapons since late 2012.The newspaper reported that the training took place at secret bases in Jordan and Turkey.So far, the Obama administration has been hesitant to sanction large-scale military aid to the rebels for fear that the arms could end up in the hands of the radical Islamists.On Thursday, several powerful Syrian rebel groups demanded al-Qaida-linked militants and a rival rebel faction stop fighting and called on the hardline Islamists to withdraw their forces within 48 hours, a statement said.The al-Qaida-affiliated Islamic State of Iraq and the Levant (ISIL) seized Azaz, about 5 km. from the frontier with Turkey, last month and has repeatedly clashed with the local Northern Storm brigade since then.A previous attempt by rebel groups to broker a truce between the two sides did not hold.The fighting prompted Turkey to close its border crossing, a lifeline for Syria’s rebel-held northern areas because it let refugees out and supplies like food and building materials in. A statement posted online by four rebel brigades on Thursday called for an “immediate cease-fire” between the two sides and called on them to submit their dispute to an Islamic court in Aleppo, about 30 km. to the south.“We ask our brothers in the faction of the Islamic State of Iraq and the Levant to withdraw their forces and equipment to their essential bases immediately,” said the statement. “We consider them above spilling the blood of Muslims or rushing to describe them as infidels and apostates.”Such restraints on the agency’s authorities stem from the US desire to see a political resolution in Syria, which requires a stalemate among opposition rebel groups, the report said.The anonymous US sources said that the CIA, in recent weeks, has sent surplus paramilitary teams to a covert Jordanian base in attempts to double the number of moderate rebel fighters receiving training and arms from the agency before returning to Syria.