Russia has invited the Democratic Union Party (PYD) officials in northern Syria to its proposed congress of Syria's various ethnic groups, a senior member told Reuters Tuesday.

"We are studying the issue and our stance has been positive so far," said Badran Jia Kurd, an adviser to the administration that governs YPG-led autonomous regions of northern Syria.The Democratic Union Party (PYD) and its armed wing, the People's Protection Units (YPG), in northern Syria are offshoots of the PKK, recognized as a terrorist group by Turkey, U.S., EU and others.

The congress is expected to be held in Russia's Black Sea resort of Sochi in mid November, but Russia's Hmeymim air base in Syria also might be used, Alexander Lavrentyev, a senior Russian negotiator on Syria said Monday.

Such a congress would focus on seeking "compromise solutions towards the political settlement" of Syria's conflict, a Russian negotiator on Syria said earlier this week.

It remains unclear which other groups or combatants in Syria's multi-sided war would take part in the congress.