"The evacuation of refugees from the Rukban camp is actually blocked because of the American side, which does not allow buses to evacuate refugees," the ministry said in a daily bulletin.
The United States has also refused to guarantee safe passage of humanitarian convoys inside a 34-mile area around the military base in southeastern Syria.
READ MORE: Russian Defence Ministry Finds 300 Fresh Graves Near Rukban Camp in Syria
The Russian ministry said a humanitarian corridor had been opened into the Al-Tanf area to allow for the voluntary return of displaced persons. The Syrian government guarantees them safety and will issue them with documents in a simplified procedure.
The Rukban camp, which houses about 40,000 displaced people, is now the US-controlled zone, which is located in the southern part of Syria, not far from Jordan.