Senior American and Russian defense officials held what the Pentagon described as an “extraordinary” video conference on Saturday to discuss Russian airstrikes that hit a garrison manned by Syrian rebels backed by the United States days earlier.
The Russian strikes hit Syrian opposition fighters on Thursday at the al-Tanf crossing, which lies on Syria’s border with Iraq. The rebels there are battling the Islamic State, the Pentagon said, and are also supposed to be covered by a partial ceasefire that the United States and Russia brokered in February.
During the videoconference on Saturday, Pentagon officials “expressed strong concerns about the attack” on forces that are fighting the Islamic State, Peter Cook, the Defense Department spokesman, said in a statement.
American officials told the Russians that their strikes had continued even after they were officially informed of allied air support underway for the rebels and that this had “created safety concerns for U.S. and coalition forces,” the statement said.
Though fighting has tapered off in many areas since the cease-fire went into effect in February, there have been fierce clashes in recent weeks in areas of northern Syria where the Islamic State and the Nusra Front are strongest. American officials have accused Russia of failing to stop the forces of Syria’s president, Bashar al-Assad, from violating the cease-fire and attacking rebel groups backed by the United States.
There was no immediate word on how Russian officials responded to the concerns expressed by American officials on Saturday. But the videoconference took place as Russia’s defense minister, Sergei Shoigu, met with Mr. Assad in Damascus and visited the Russian air base in Syria, The Associated Press reported.
Since the Russian air campaign in Syria began in September, it has helped Mr. Assad’s forces reclaim territory, reversing the fortunes of a regime that at this time last year appeared to be in an increasingly perilous position.
American-backed rebel forces, in contrast, have continued to struggle on the battlefield against both Mr. Assad’s forces and the Islamic State, and more than 50 State Department diplomats recently signed an internal memo sharply critical of the Obama administration’s policy in Syria.
The memo pressed for American military strikes against Mr. Assad’s government to stop what it said were persistent violations of the cease-fire. American policy has been “overwhelmed” by the violence in Syria, the memo said.