Obama's request to Congress for $500 million in training and arms to the militants came as ISIL terrorist group is threatening to overwhelm neighboring Iraq.

The train-and-equip mission would be overseen by the Pentagon and would mark a significant expansion of previous covert effort to arm the insurgents fighting forces loyal to Syrian President Bashar Assad.

Obama administration officials claim the US has grown increasingly confident in recent months about its ability to distinguish the moderate rebels from the more extremist elements that include the al-Qaeda-inspired Islamic State of Iraq and the Levant, or ISIL, which has stormed into Iraq and captured much of the northern part of the country.

The Syria program is part of a broader $65.8 billion overseas operations request that the administration sent to Capitol Hill on Thursday. The package includes $1 billion to help stabilize nations bordering Syria that are struggling with the effects of the civil war. It also formalizes a request for a previously announced $1 billion to strengthen the US military presence in Central and Eastern Europe amid Russia's threatening moves in Ukraine.

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