The secret order, referred to as an "intelligence finding," allows for more extensive clandestine non-lethal support, including intelligence, by the CIA and other agencies than previously acknowledged, the officials told the networks.
It was unclear when Obama signed the authorization, but officials told CNN he signed it within the past several months.
It was additionally unclear precisely what type of support the intelligence finding authorizes, the networks said.
During the Libyan civil war last year, Obama signed a similar directive authorizing covert assistance to rebels battling Libyan leader Moammar Gadhafi.
That directive sent CIA and other covert operatives to Libya as part of an escalating U.S. effort to vet the rebels working to oust Gadhafi and lay the groundwork for funneling U.S. aid to the insurgents, a report by the National Journal said at the time.
The idea was evidently to get CIA operatives into position to make contact with Libya's disparate insurgents and begin orchestrating the logistics of providing weaponry, money and other forms of aid to the fighters, the National Journal said.
The Obama administration has ruled out arming Syria's rebels for now, and Secretary of State Hillary Clinton has said the administration was providing only non-lethal assistance, such as communications equipment.
The White House, State Department and CIA had no immediate comment on the reports.
The White House also announced Thursday it was adding $12 million in humanitarian aid, bringing the total aid allocation for Syrian refugees to $76 million.
Officials said the money will help Syrian neighbors, including Iraq, Lebanon and Turkey, who are providing temporary homes for those who have left Syria.
The intelligence-finding reports came a day after the U.S. Treasury Department said it gave the Washington-based Syrian Support Group clearance to provide direct financial assistance to the Free Syrian Army in a new Obama administration bid to support Syria's opposition.
The department's Office of Foreign Assets Control approved a license July 23 letting the group engage in "otherwise prohibited" financial activities with the rebel forces, said the license, seen by United Press International.
The license -- which expires July 31, 2014 -- requires detailed reports to the State Department's little-known Office of Terrorism Finance and Economic Sanctions. The license prohibits shipment of military equipment or hardware, but lets the group send money.
U.S. officials have told CNN Washington is cooperating with countries arming the rebels, including Saudi Arabia and Qatar, to help find groups worthy of aid.
Diplomatic sources have also told CNN Washington is providing intelligence on Syrian troop movements, which is then passed to rebel groups.
U.S. and European officials have commented in recent weeks they have seen visible improvements in how Syrian rebel groups are fighting.
Foreign policy experts urged Washington Wednesday to increase its support of the armed opposition.
"At this point, given the direction of the conflict, I think that what we need to do is assess which groups could we and should we arm at what point, and make that decision," Andrew Tabler, a senior fellow on Arab politics at the Washington Institute for Near East Policy think tank, told the Senate Foreign Relations Committee.
"I think that we're actually at that decision, given where the conflict is going," Tabler said.
In Syria, neighborhoods of Aleppo remained under intense fire from regime helicopters and shells Thursday in the 13th day of fighting between Syrian and opposition forces.
International observers saw warplanes targeting rebels in the city Wednesday, a spokesman for the U.N. mission in Syria said, as the Syrian army sought to press forward with its counteroffensive to retake control of the northern Chicago-size city of about 2.5 million that fell into rebel hands last month.
Assad called his armed forces "heroes" in a statement Wednesday, adding, "The army is engaged in a battle on which the destiny of the nation and its people rests."
Assad has not been seen in public since a bombing killed his powerful defense minister brother-in-law and three other senior security chiefs in Damascus July 18.
Assad did not attend the funeral of Assef Shawkat, married to his sister Bushra, but appeared on state TV swearing in a replacement defense minister.
The U.S. State Department condemned Assad's comments.
"It's cowardly, quite frankly, to have a man hiding out of sight, exhorting his armed forces to continue to slaughter the civilians of his own country," spokesman Patrick Ventrell said.