The latest round of talks between US and Russian military officials has brought the two sides closer to an understanding on air safety over Syria. An agreement could be "signed and implemented in the coming days."
A memorandum of understanding between Russia and the United States could be implemented in the near future, according to a US official.
"We are nearing completion of a memorandum of agreement that would set up procedures to enhance air safety," a US official told the AFP news agency, speaking on condition of anonymity. "It could be signed and implemented in the coming days."
A third round of talks between US and Russian military officials in a secure video conference on Wednesday led to progress in discussions aimed at promoting safe air operations over Syria, according to the Pentagon.
When Russian jets began airstrikes in Syria on September 30, concerns grew of a possible accident involving US and Russian jets. The US claims Russian aircraft have come within miles of drones and piloted US fighter jets.
The US has said it will not change its air operations against forces with the so-called "Islamic State" (IS) in Syria. Washington has also refused to cooperate with Moscow because of Russia's support for Syrian President Bashar al-Assad. Talks with Russia have been limited to basic air safety.
"We have not, for our part, and will not agree to cooperate with Russia as long as they continue to pursue a misguided strategy," said US Defense Secretary Ash Carter, speaking at a meeting of US Army leaders in Washington on Wednesday.
In some of the strongest comments since Russia began its airstrikes over Syria, Carter accused Russia of "unprofessional behavior."
'No one can do this alone': Steinmeier
Russian Foreign Minister Sergey Lavrov said proposals had been made to the United States for a high-level military delegation to be sent to Moscow to discuss coordination in the military operations, but that this had been declined by Washington.
German Foreign Minister Frank-Walter Steinmeier, who is due in the Middle East for talks on the situation in Syria in the coming days, warned the US and Russia to avoid escalating the conflict and called for a regional political solution.#
"No one can do this alone. We need everyone for a political solution," he said. "We especially need the regional partners, the neighbors like Turkey, Iran and Saudi Arabia. We need Europe and the US. But given recent developments we know that it will not happen without Russia."