Washington: Defence Secretary Ash Carter says the US is nearing an agreement in its discussions with Russia about flight safety in the skies over Syria, and talks may conclude soon.

Carter says Pentagon officials and Russian leaders will have their third video-conference on the issue today, as US-led coalition and Russian aircraft try to avoid collisions when they launch airstrikes into Syria. Carter says the talks on professional conduct in the air are progressing.

Army Col Steve Warren, US military spokesman in Baghdad, says US and Russian aircraft came within sight of each other over Syria on Saturday, but they were miles apart and the pilots behaved professionally. He says more often Russia aircraft have flown near US drones, perhaps to get a closer look at the high-tech aircraft.