Six months after it was first hinted at, and a month after widespread reports surfaced, the United Nations, Britain, and France have all just confirmed the use of chemical weapons in Syria. Yet, there has been no U.S. response to Syria’s increasingly clear violation of President Obama’s publicly stated red line. This lack of action raises serious questions about the resoluteness of U.S. policy when it comes to another potential “game-changer” in the region: Iran developing a nuclear weapon.

Rather than deterring Syria or Iran from using or pursuing illicit weapons, the administration’s red lines appear to be eroding U.S. credibility and national security.  The lesson learned from Syria is that preventing a nuclear Iran will require an actionable and verifiable red line. This should include a credible mechanism for assessing Iran’s progress toward the red line and warning of its crossing.