US Secretary of State claims to have gathered the support of "a number" of Arab League nations for a "strong international response" following talks in Paris yesterday.
Speaking ahead of his London summit with Foreign Secretary William Hague, Mr Kerry said a "global red line" had been crossed.
"All of us agreed, with not one dissenter, that Assad's deplorable use of chemical weapons, which we know killed hundreds of innocent people, including at least 426 children, on this occasion, this one occasion, crosses an international, a global red line.
"What the United States is seeking - not alone but with others, an increasing number - is to enforce the standard with respect to the use of chemical weapons."
More top news
Edinburgh and its institutions have been at heart of the Union since it came about in 1707, here we look at the city's history.
In Berwick-upon-Tweed - the town at the northern-most tip of England - history has taught them that no border necessarily lasts forever.
His car was about to get towed away. But he had other ideas.