Will the United States join Britain and France in responding to Syria's use of chemical weapons?

Britain and France have written separately to Secretary General Ban Ki-moon of the United Nations that there is credible information suggesting Syria’s government has used chemical weapons in the civil war on multiple occasions since last December, diplomats said Thursday. ...

The assertions by Britain and France are stronger than that of the United States, which has said that it is assessing claims of chemical weapons use in Syria, but has not come to any conclusions. President Obama has said the use of such weapons in the war would constitute a “game changer” that could lead to an American military response.