Kerry addressed protesters in London chanting "Keep your hands off Syria," and cited what he said are some similar anti-war sentiment in the U.S.
"I think it would be good to hear people saying to a dictator, 'Keep your hands off chemical weapons that kill your own people. Protect your own people,'" he said. "It's important for us to stand up as nations for civility and against actions that challenge notions of humanity and decency and appropriate international behavior."
He cited the genocide in Rwanda and the Holocaust as examples of "moments of history when large numbers of people have been killed because the world was silent."