The official did not elaborate any further on the exact timing other than to say it would happen "soon." A second official said the agreement that emerges would cover all aircraft that are part of the U.S.-led coalition fighting ISIS.
Both Russia and the United States "have a consensus on the technical aspects" of how parties to the agreement will conduct themselves to assure the safety of their pilots, but they still have some final details over the wording of the agreement to work out, the official said.
That development came the same day that U.S. and Russian defense officials held their third video conference aimed at reaching an understanding governing aerial operations since Russian military jets began their own bombing campaign in Syria.
The video conference "focused on steps that can be taken by Russian and counter-ISIL coalition aircraft to promote safe flight operations over Syria," Pentagon spokesman Capt. Jeff Davis said in a written statement. "Progress was made during the discussions, which were professional and focused narrowly on the implementation of specific safety procedures."
It also came just a few days after a U.S. and Russian jet came within miles of each other.
Major General Igor Konashenkov, a spokesman for the Russian Defense Ministry told reporters Wednesday the Russian jet approached the U.S. jet on Sunday to identify it and "not to scare it," saying the two jets came as close as approximately two miles of each other.
In a briefing with reporters Tuesday, Col. Steve Warren, a spokesman for the U.S.-led coalition, said the two planes were "close enough for them to get some visual contact, but they were miles apart," perhaps as much as 10 to 20 miles, according to initial reports.
Warren said initial reports are always updated but that the jets certainly were close to each other.
Russia has said its military campaign in Syria was primarily intended to battle ISIS and other extremist groups operating there, but it has since focused on targeting rebel groups, including some supported by the United States, battling President Bashar al-Assad's forces.
In remarks to the Association of the United States Army conference in Washington Wednesday, Defense Secretary Ashton Carter called Russia's backing of its close ally Assad, whom the United States has called on to leave office, a "fundamental strategic mistake" that Moscow was making.
Those actions are of "great concern" to the United States, and are a main reason why the current military discussions with Russia are narrowly focused on aerial operations as opposed to broader military discussions, one of the officials said.
Carter said the United States "will not agree to cooperate with Russia as long as they continue to pursue a misguided strategy," and that the aerial bombardment by the coalition fighting ISIS inside Syria and Iraq would continue.
"We, for our part, will continue to prosecute the counter-ISIL campaign with the same determination and in the same battle space as we have since it started in Syria," he said.