Russian news agencies quoted Foreign Ministry spokeswoman Maria Zakharova as saying that a U.S. intervention against the Syrian army “will lead to terrible, tectonic consequences not only on the territory of this country but also in the region on the whole.”

She said regime change in Syria would create a vacuum that would be “quickly filled” by “terrorists of all stripes.”

U.S.-Russian tensions over Syria have escalated since the breakdown of a cease-fire last month, with each side blaming the other for its failure. Syrian government forces backed by Russian warplanes have launched a major onslaught on rebel-held parts of the northern city of Aleppo.

Syrian troops pushed ahead in their offensive in Aleppo on Saturday capturing the strategic Um al-Shuqeef hill near the Palestinian refugee camp of Handarat that government forces captured from rebels earlier this week, according to state TV. The hill is on the northern edge of the Aleppo, Syria’s largest city and former commercial center.