The United States is willing to work with Russia on establishing “no-fly zones” in Syria, the top US diplomat said Wednesday, ahead of President Donald Trump’s meeting with Russian leader Vladimir Putin later this week.

In a wide-ranging statement, Secretary of State Rex Tillerson said Russia had a “special responsibility” to help create stability on the ground — or risk hobbling the fight against ISIS.

Citing past cooperation in creating deconfliction zones in Syria, Tillerson made a strong case for both countries — in spite of their “unresolved differences on a number of issues” — to work together in Syria.

“The United States is prepared to explore the possibility of establishing with Russia joint mechanisms for ensuring stability, including no-fly zones, on the ground ceasefire observers, and coordinated delivery of humanitarian assistance,” he said.

Tillerson issued his statement before joining Trump in Europe, where the US leader will meet Putin for the first time on Friday on the sidelines of a G20 summit in Hamburg, Germany. Syria will loom large in their discussions.

It also came as US-backed fighters inched forwards in Raqqa’s Old City, in what Washington sees as a milestone in the campaign to defeat ISIS in its de facto Syrian capital.

He said that Russia, as an ally of Bashar Assad and a participant in the conflict, “has a responsibility to ensure that the needs of the Syrian people are met and that no faction in Syria illegitimately re-takes or occupies areas liberated from ISIS’ or other terrorist groups’ control.”

Tillerson added that Russia has “an obligation to prevent any further use of chemical weapons of any kind by the Assad regime.”