WASHINGTON • Russia and the United States are set to renew talks to avoid accidents in Syrian airspace as the two countries conduct separate bombing campaigns, said a US official.

The Pentagon expressed alarm last week after Russia failed to quickly answer proposals made during initial talks, even as it launched cruise missiles from the Caspian Sea and repeatedly violated Turkish airspace.

But on Friday, Pentagon press secretary Peter Cook said Moscow had filed an appropriate response.

"The Department of Defence (DoD) has received a formal response from the Russian Ministry of Defence regarding DoD's proposal to ensure safe air operations over Syria," Mr Cook said.

"Department leaders are reviewing the Russian response and talks are likely to take place as soon as this weekend."

US officials were furious after Russia gave them a vague, verbal "heads-up" only about an hour before Moscow launched its bombing campaign on Sept 30.

The two countries had "deconfliction" talks the next day via video conference, which were aimed at ensuring that Russian warplanes did not cross paths with drones and US-led coalition jets.

Talks centred on basic safety measures, including which language air crews should communicate in and how much space planes should leave one another.

Russian planes have flown near a US drone, officials said, and the US military has had to reroute some flights to avoid any close calls.

AGENCE FRANCE-PRESSE