On the heels of Secretary of State John Kerry saying that Israel had not provided evidence that Syria used chemical weapons against rebels, U.S. intelligence officials admitted they believe with “varying degrees of confidence” that Syria has used chemical weapons.

The White House said that the sarin nerve agent had been used on what they termed a “small scale”. The announcement was in a letter to members of Congress.

“Our intelligence community does assess, with varying degrees of confidence, that the Syrian regime has used chemical weapons on a small scale in Syria, specifically, the chemical agent sarin,” read a letter from Miguel Rodriguez, White House director of the office of legislative affairs.

The White House has previously said that use of chemical weapons would be a “red line” but that the current evidence collected is not sufficient proof.

US Defense Secretary Chuck Hagel told reporters that the use of Sarin “violates every convention of warfare.” Secretary of State Kerry now says there have been two cases of sarin being used in Syria. The UK has collected samples from inside Syria that have been tested and are positive for sarin.