DAMASCUS — Syria’s government and its ally Russia accused Washington of concocting a ‘‘provocation’’ in Syria, which would then be blamed on President Bashar Assad’s government as alleged use of chemical weapons to justify an attack. Syria’s Foreign Ministry said it rejects US allegations Syria was preparing for a chemical weapons attack as ‘‘completely baseless.’’

It said the objective was to ‘‘justify a new aggression on Syria under ill-founded pretexts,’’ similar to what happened in April, when the United States struck a Syrian air base it said had been used to stage a chemical attack, killing nearly 90.

Earlier this week, the White House warned that Assad was preparing for another chemical attack and said the Syrian ruler would ‘‘pay a heavy price’’ if he unleashes it.

Also Thursday, a Russian Foreign Ministry spokeswoman said Moscow has information that Syrian rebels fabricated videos to accuse Damascus of a chemical attack. She said such action could be aimed at derailing the next round of Syriam peace talks — brokered by Russia, Turkey, and Iran — next week.

Associated Press