Sergei Lavrov said the US had broken its promise to separate the powerful Jabhat Fateh al-Sham (formerly known as al-Nusra Front) and other extremist groups from US-backed moderate rebels.
“They still are not able or willing to do this,” he said.
“We believe the plan was to spare Nusra.”
He added: “They [have] never touched Nusra anywhere in Syria.”
Mr Lavrov was speaking to Stephen Sackur on BBC World News TV on the first anniversary of the beginning of the Russian air campaign in Syria.
He accused the West of staying quiet about civilian suffering in Aleppo when it was expecting the city to fall to the rebels after the Nusra group moved in and cut supply lines to the civilian population.