A U.S.- or Turkish-backed attack on Islamic State in the Syrian city of Raqqa would be illegitimate unless coordinated with President Bashar al-Assad's government, the Syrian chief negotiator at peace talks in Geneva said on Friday.
"Any military presence on our territory without the approval of the Syrian government is an illegitimate presence," Bashar al-Ja'afari told reporters after meeting U.N. envoy Staffan de Mistura.
French Defence Minister Jean-Yves Le Drian said on Friday the battle to recapture Raqqa would restart in the coming days.
Ja'afari said nobody could claim to be fighting Islamic State without coordinating with Iraq and Syria.
"Those who are truly fighting Daesh (Islamic State) are the Syrian Arab army with the help of our allies from Russia and Iran.
"Direct U.S. military intervention in Syrian territory as well as arming factions in Syria and encouraging them to challenge the authority of the state does not serve the fight against terrorism," he said.
The U.S.-backed Syrian Democratic Forces (SDF) have reached the entrance to the Tabqa dam where they are clashing with Islamic State, Jihan Sheikh Ahmed, an SDF spokeswoman, said on Friday.
U.N. Syria humanitarian advisor Jan Egeland told Reuters on Thursday there were contingency plans for the civilian population of Raqqa.
"There are hundreds of thousands of people in the Raqqa area and of course those would all be at risk when the fighting is bound to intensify," Egeland said.
Ja'afari said countries backing rebel groups in Syria, such as Britain, France, Turkey and Qatar, were sponsors of terrorism, and said a rebel offensive was designed to disrupt peace talks in Geneva and Astana.
"All the terrorist attacks, as I said, are pushing everybody toward a total failure and fiasco in the political and diplomatic process," he told reporters, adding his delegation would never walk away from the talks