Hours after the Kremlin condemned Turkey’s decision to shoot down the warplane for entering its airspace, Rubio warned against letting Russia get the upper hand.

“It’s important for us to be very clear that we will respond and defend Turkey if they come under assault from the Russians. Otherwise the entire NATO alliance comes into question,” Rubio, who is running for president, said on Fox News.

“If Russia believes that they can respond and retaliate against Turkey because NATO is not going to do anything about it, what they are basically doing is making the argument that NATO is no longer viable, that it is a feckless alliance.”

The incident was the first time a NATO member has shot down a Russian target since the Cold War, and it threatened to escalate the political tensions surrounding the 4-year-old civil war in Syria.