U.S. Secretary of State John Kerry wants all aircraft over key humanitarian routes in northern Syria grounded in order to give peace a chance.

Kerry told the U.N. Security Council that such a step could restore credibility to efforts to end the five-year civil war and "give a chance for humanitarian assistance to flow unimpeded."

A U.S.-Russian cease-fire agreement reached on Sept. 9 has all but collapsed. And the U.N. suspended aid deliveries after a strike on a humanitarian convoy this week that killed a dozen people.