U.S. Secretary of State John Kerry demanded on Wednesday that Russia and the Syrian government immediately halt flights over Syrian battle zones, in what he called a last chance to salvage a collapsing cease-fire and find a way "out of the carnage.

An impassioned Kerry faced off with Russian Foreign Minister Sergey Lavrov at the U.N. Security Council in New York, during a tense televised showdown, saying the bombing of an aid convoy in Syria raised "profound doubt whether Russia and the Assad regime can or will live up to" cease-fire obligations.

Speaking before Kerry, Lavrov told the 15-member Security Council: "One needs to refrain from emotional instincts, from rushing to the microphone immediately to comment on something; a probe should be conducted (into the aid convoy attack)."