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
Two pilots have been arrested on suspicion of being under the influence of alcohol as they prepared to fly from Scotland to the New York.
Two teenagers have been arrested on suspicion of drugs offences following the death of a 17-year-old youth who collapsed at Leeds Festival.
Theresa May will gather Cabinet ministers together on Wednesday to discuss her plans for Brexit.