Russian Foreign Minister Sergei Lavrov said Washington's offer to cooperate in Syria is a "step in the right direction" but further information is needed about the U.S. proposal to create "no-fly zones" there.
"We have asked, but we haven't got an answer to the question of what no-fly zones are envisioned, because there has never been any talk of them," Lavrov said during a visit to Paris on July 6.
Russia is currently pushing a plan along with Iran and Turkey to establish four "de-escalation zones" on the ground where air strikes would be halted.
U.S. Secretary of State Rex Tillerson on July 5 said the United States is "prepared to explore the possibility of establishing with Russia joint mechanisms for ensuring stability, including no-fly zones."
Tillerson's statement came ahead of the first meeting between President Donald Trump and his Russian counterpart, Vladimir Putin, on the sidelines of the G20 summit in Hamburg on July 7.
Shortly after taking office, Trump said he would like to establish "safe zones" in Syria where Syrian civilians would be safe from fighting in the civil war, but he has never offered a detailed plan.