"Direct aggression" by the United States toward the Syrian government and armed forces would lead to "frightening, tectonic shifts" in the Middle East, RIA news agency cited Russian Foreign Ministry spokeswoman Maria Zakharova as saying on Saturday.

Russia and the United States back opposing sides in the Syrian conflict.

A U.S.-Russian brokered ceasefire in Syria recently fell apart, and Russian war planes on Saturday struck rebel-held areas north of the Syrian city of Aleppo.