PLEASE NOTE: EDIT CONTAINS MATERIAL THAT WAS ORIGINALLY 4:3
Amateur video appears to show Syrian rebels in action.
The video, posted on social media website and not independently verified by Reuters, purportedly shows them firing on government troops in a suburb of Damascus.
Now the U.S. says it's authorised direct military support for the rebels fighting to oust President Bashar al-Assad.
The White House didn't specify if that would include weapons.
An official speaking on condition of anonymity said it would - a reversal of President Barack Obama's stance so far.
Obama's decision was revealed in a media conference call with U.S. Deputy National Security Advisor Ben Rhodes.
(SOUNDBITE)(English) BEN RHODES, U.S. DEPUTY NATIONAL SECURITY ADVISOR, SAYING:
"The President has made a decision about providing more support to the opposition. That will involve providing direct support to the SMC (Supreme Military Council). That includes military support."
The arrival of thousand of Iran-backed Hezbollah fighters to help Assad's forces fight the rebels has shifted momentum in Syria's two-year-old war.
The rapid change has worried U.S. and European officials who were due to meet rebel commanders on Friday in Turkey.
Syria rebels to get U.S. military help (1:20)
June 14 - The U.S. says it is to step up military aid to Syria's rebels after determining the use of chemical weapons by government forces. Paul Chapman reports. ( Transcript )