MOSCOW — The Foreign Ministry here expressed surprise on Monday over an American warning to Russia against escalating the conflict in Syria, saying that the Kremlin’s Syrian policy — in particular furnishing military aid to help the government confront extremist forces — had been consistent for years.

“We have always supplied equipment to them for their struggle against terrorists,” Maria V. Zakharova, the Foreign Ministry spokeswoman, said in an interview. “We are supporting them, we were supporting them and we will be supporting them” in that fight.

The sharp exchanges over Russian military aid to the Syrian government appeared to have dampened a brief spirit of cooperation, starting in early August, when Russia, the United States and Saudi Arabia agreed on a renewed effort to reach a political solution to the Syria crisis.

Some analysts see any possible Russian move to strengthen military aid now as a maneuver by President Vladimir V. Putin to embarrass the United States.