CNN aired graphic videos of victims that it said were shown to select US lawmakers as part of a push to shore up support for a strike on Syria.
The broadcaster said the 13 videos were shown to members of the Senate Intelligence Committee who were told they depict victims of an August 21 chemical weapons attack in the war-torn country.
Excerpts depict convulsing children and men sprawled on the floor apparently vomiting and foaming at the mouth.
Another shows what appear to be dead bodies of dozens of Syrians, including children, lying side by side. Yet another shows a man holding the apparently lifeless body of a little boy.
The senators were told by the intelligence community that the videos had been verified, according to CNN.
However, the broadcaster said it could not independently verify the authenticity of the material and stressed that the videos do not show who is responsible for the attack.
But it said it was able to verify that the US administration is showing the videos to members of Congress as part of their effort to convince lawmakers of the need for a limited military strike on the Syria.
The videos - many of which CNN said were previously posted online - surfaced as President Barack Obama prepares to personally make his case to the American people.
The White House has announced that President Barack Obama would tape interviews on Monday (local time) with three network news anchors, as well as with PBS, CNN and Fox.
The interviews, to air that night, will precede an address by Obama on Tuesday.
Setting the stage Sunday, the White House's chief of staff, Denis McDonough, will hit the morning television talk shows.
In Congress, meanwhile, Secretary of State John Kerry, Pentagon chief Chuck Hagel and others senior administration officials will hold a briefing for all members of the House of Representatives on Monday, a White House official said Saturday.
That will be followed by a briefing Wednesday for all members of the Senate.