Naval Air Station Sigonella, Italy, Reuters—Russia moved on Tuesday to resume military talks with the United States aimed at setting rules for air-to-air conduct over Syria, a US official said, as the former Cold War foes carry out parallel, uncoordinated campaigns of airstrikes.

The discussions on ways to keep the US and Russian aircraft from clashing over Syria, launched last week, have gained urgency after the US and NATO denounced Russia for violating Turkish airspace.

Turkey, a NATO ally, threatened to respond, raising the prospect of direct confrontation.

During a trip to Europe, US Defense Secretary Ash Carter described the need to resume talks as urgent, and condemned Russia’s “seriously irresponsible and unprofessional” violation of Turkish airspace.

Hours later, a US official, speaking on condition of anonymity, told reporters Moscow had indicated it was willing to resume talks but no date had been set.

Russia’s deputy defense minister, Anatoly Antonov, was quoted by the Tass news agency on Tuesday as saying the Russian military agreed in principle with the proposals made by the US on coordinating military flights.

But he was quoted as saying differences remained, that the potential for collaboration was “much wider” than what Washington was offering, and that Russia had made its own proposals, though he did not specify what they were.

“To our regret, the Americans are for now saying that our co-operation should be limited to technical questions concerning our pilots when they carry their missions,” said Antonov.

“The Americans have handed us a document, which we are working on. The general staff supports the document in principle.”

“Strategic confusion”

He said the two countries would hold a second joint video conference on the subject in the “coming days”.

“But it would be better if our (US) colleagues came to see us at the Defense Ministry so we could talk face to face about all the problems we face,” Antonov was quoted as saying.

The US proposal includes basic safety protocols, such as maintaining a safe distance between US and Russian aircraft and using common radio frequencies for distress calls, officials say, adding they would be similar to civil aviation.

Pentagon spokesman Peter Cook said the US awaited a formal response from Russia on the US proposals.

“We stand ready to meet again to continue our earlier discussion as soon as possible,” Cook told reporters traveling with US defense secretary in Italy, declining to offer further details.

Carter expressed frustration that Russia, after calling for talks with the US, had let so much time elapse before getting back in touch on the US proposals for air conduct.

“That may be a further sign of their strategic confusion, I don’t know,” he said, speaking to reporters earlier in Spain.

The US and Russia say they have the same enemies – the Islamic State of Iraq and Syria (ISIS) group of Sunni Muslim militants who have proclaimed a caliphate across eastern Syria and northern Iraq.

But Washington fiercely opposes Moscow’s support for Syrian President Bashar Al-Assad and accuses Moscow of mainly targeting other insurgents who oppose Assad, rather than ISIS.

Carter said Moscow’s strategy of bolstering Assad would backfire.

“In Syria, they are going to be checked in the first instance by the backlash that they’re going to get on account of siding with Assad against everyone else,” Carter said.