A US defense official said Wednesday that his country and Russia could soon sign a pact establishing safety protocols in the skies above Syria as both powers carry out separate bombing campaigns.

A US defense official said Wednesday that his country and Russia could soon sign a pact establishing safety protocols in the skies above Syria as both powers carry out separate bombing campaigns.

"We are nearing completion of a memorandum of agreement that would set up procedures to enhance air safety," the official said, speaking on condition of anonymity.

"It could be signed and implemented in the coming days."

The official's comments came shortly after Russia and the United States held a third round of video talks to decide rules so pilots don't inadvertently fly into each other.

"Progress was made during the discussions, which were professional and focused narrowly on the implementation of specific safety procedures," Pentagon spokesman Captain Jeff Davis said.

The US-led coalition has for more than a year been conducting regular drone and plane strikes in Syria and Iraq, allegedly targeting the Takfiri group, ISIL (so-called Islamic State in Iraq and Levant).

Under the request of the Syrian government, Russia launched its own military campaign against ISIL targets since September 30.

So far, there have been no major incidents in the Syrian skies, though Pentagon officials said coalition planes have had to change course to avoid being in the same space as Russian jets.

And on Tuesday, Colonel Steve Warren, the spokesman for the US-led coalition, told reporters that coalition and Russian planes came close enough to establish visual contact.

"There's always going to be some risk if there are uncoordinated actors in the battle space," he said.