美国说俄罗斯必须证明叙利亚停火能够奏效

A senior U.S. official says it is up to Russia to demonstrate that a cease-fire plan for Syria can still work.

The official said high-level meetings were planned with Russia "to try to get a sense from them about where they think this can go from here." Consultations were also ongoing with envoys from the 19-nation International Syria Support Group and the U.N. Security Council.

French Foreign Minister Jean-Marc Ayrault, who was due to attend an ISSG meeting Tuesday, said the U.S.-Russian cease-fire deal “remains the only hope to resolve the conflict."

The truce was meant to pause fighting between the Syrian government and rebels, limit Syrian airstrikes that in the past have been blamed for killing civilians, and to allow for delivery of humanitarian aid. But as with earlier agreements, both sides accused the other of violations and the pact had largely fallen apart after a week.

On Monday the United Nations said a joint aid convoy with the Syrian Red Crescent was bombed west of the Syrian city of Aleppo, killing or wounding many humanitarian workers.

It remains unclear whose aircraft struck the convoy. The Pentagon said the U.S.-led coalition was not involved, and a senior U.S. official said there were only two other possibilities, referring to Syria and Russia.