Rebel fighters are gathered to prepare the launch of a rocket in the Saif al-Dawla district of the northern Syrian city of Aleppo, on April 21, 2013. (MIGUEL MEDINA/AFP/Getty Images)
WASHINGTON -- The Obama administration says U.S. intelligence has a "varying" amount of confidence that Syria's government has twice used chemical weapons in its civil war.
But officials say more definitive proof is needed, and that the U.S. isn't ready to escalate its involvement in Syria.
President Barack Obama has repeatedly asserted that Syria's use of chemical weapons, or the transfer of its stockpiles to a terrorist group, would cross a "red line."
By saying it needs more proof, the administration may be looking for additional time in which to craft a response.
The White House disclosed the new intelligence today in letters to two senators.
Defense Secretary Chuck Hagel, traveling in Abu Dhabi, also discussed it with reporters.
In its letter, the White House said there's evidence that Syria used the chemical agent sarin "on a small scale" in Syria.
Shortly after the letter was made public, Secretary of State John Kerry said on Capitol Hill that there were two instances of chemical weapons use.
It's not clear what quantity of weapons might have been used, or when.
And there's no word on what casualties might have resulted.
A senior defense official says the White House letter isn't an "automatic trigger" for policy decisions on the use of military force.