The official said that "he's seen signs that Russian military commanders in Syria have been quietly coordinating with Iran's Islamic Revolutionary Guard Corps (IRGC) on long-term plans to pressure the United States to withdraw its forces" from Syria, Al-Monitor wrote. 

"There's a confluence of interests between those three groups, the Iranians, the Russians, and the Syrians. I see evidence of operational-level planning between mid-level Quds Force leadership that's operating in Syria [and] Russian forces that are operating in Syria," the anonymous official told the outlet. 

According to the official, the Russian-Iranian coordination in Syria centers around "collaborative planning, collaborative understanding, and intelligence sharing… [at the] mid-level to upper echelon" of Moscow and Tehran's armies. 

"Frankly, [it's] the same sorts of things that we would do with our partners in the face of something we were trying to accomplish. We see them doing that on their side, as they try to think about how they sync the different things that different arms of them are doing in order to put that pressure on us," the source added.