Tillerson said in a statement released in Washington late Wednesday that the United States was "prepared to explore" the establishment with Russia of "joint mechanisms" for Syria, now into its sixth year of warfare.

This could include "no-fly zones, on-the-ground ceasefire observers, and coordinated delivery of humanitarian assistance," Tillerson said.

At the G20 in Hamburg this Friday, face-to-face talks are expected between US President Donald Trump and Russian President Vladimir Putin.

A "special responsibility" to help stabilize Syria fell on Russia, said Tillerson, referring to Moscow's military backing for Syrian President Bashar al-Assad.

"If our two countries work together to establish stability on the ground, it will lay a foundation for progress on the settlement of Syria's political future," said Tillerson. 

"Russia also has an obligation to prevent any further use of chemical weapons of any kind" by Syrian President Bashar al-Assad's regime, he added.

Assault on Raqqa

His statement came as US-backed forces pressed their assault on the "Islamic State" group's hub, the city of Raqqa, where up to 100,000 people are trapped in desperate conditions, according to the United Nations.

Tillerson said Islamic State had been "badly wounded" and might be on the "brink of complete defeat."

"In order to complete the mission, the international community, and especially Russia, must remove obstacles to the defeat of ISIS [Islamic State]," he said.

Ipj/bw (AP, Reuters, AFP)