Facing Allies’ Doubt, John Kerry Voices Confidence in Syria Cease-Fire

MUNICH — Secretary of State John Kerry, facing both anger and skepticism from European allies about the willingness of the United States to intervene more deeply in the Syrian civil war, promised on Saturday to help close off the routes migrants were taking to Europe and warned Russia that its military effort to prop up President Bashar al-Assad of Syria would ultimately fail.

Mr. Kerry’s comments at the annual Munich Security Conference here came a day after he announced an agreement to send humanitarian relief to besieged cities in Syria and a “cessation of hostilities” within a week.