U.S. conveyed concerns to Russia over Syria troop collision - White House official

The United States has conveyed its concerns to Russia over an incident in Syria in which several U.S. troops were injured when a Russian military vehicle collided with theirs, National Security Adviser Robert O'Brien said on Friday.

"It's been communicated to them (Russia) very clearly," O'Brien told a White House news conference. "It's been communicated at the appropriate level."