In an interview aired Friday on BBC World News, Lavrov said Washington had vowed to "take as a priority an obligation to separate the opposition" from the former Al-Qaeda affiliate once known as Al-Nusra Front, but that it had not done so.

"We have more and more reasons to believe that from the very beginning the plan was to spare Nusra and to keep it just in case for Plan B or stage two, when it would be time to change the regime," Lavrov said.

Moscow has repeatedly accused the US of failing on its commitment to persuade rebel forces to distance themselves from terrorist groups such as Al-Nusra, which changed its name to Fateh al-Sham Front in July after renouncing its ties to Al-Qaeda.

A short-lived truce brokered by Moscow and Washington earlier this month could have led the two countries to coordinate strikes against terrorists, but the deal fell apart as both sides blamed each other for its failure.
   
Russia has said it would continue its Syrian bombing campaign in spite of US warnings that Washington would suspend talks unless Moscow stopped its assault on Aleppo.

In a phone call with US Secretary of State John Kerry on Friday, Lavrov stressed Moscow's "readiness to continue to consider additional possibilities" to work with the United States on normalising the situation in Aleppo, Russia's foreign ministry said in a statement.

Lavrov also stressed Russia "remains open for dialogue with the United States on all key issues" regarding Syria, the statement said; AFP reported.

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