The talks are expected to be held on November 18 in the Russia city of Sochi, just 10 days before the UN-sanctioned conference.
Russia to hold Syrian peace talks ahead of UN meeting
The main Syrian opposition body said on Thursday that Russian-sponsored Syrian peace talks later this month undermine the UN-led diplomacy and attempt to reinstate President Bashar Al Assad's government.
"We, in the High Negotiations Committee (HNC), insist on rejecting discussion of Syria's future outside the legal, UN framework," the HNC said.
Russia hopes that all Syrian opposition groups will attend the conference in Sochi on November 18 despite some objections by opposition, Russian deputy foreign minister Mikhail Bogdanov said on Thursday.
The leading Syrian opposition group is calling on the United Nations to retake charge of the peace process, saying Russia is imposing its own rules for Syria, where more than 400,000 people have been killed in a six-year-long civil war.
Asked if Moscow still hoped to see opposition groups like the High Negotiations Committee, which has refused to come, attending, Mr Bogdanov was hopeful.
"We hope that everyone who believes that the fate of the country, its unity, its territorial integrity and its sovereignty are important will participate." he said.
Moscow has also invited the Kurdish authorities in the north of Syria to the Syrian Congress on National Dialogue, which would mark the first time Syria’s main Kurdish group would meet in peace talks.
More than 30 Syrian groups and political parties are expected to attend the talks held on November 18, exactly 10 days before the UN convenes its own talks between the government and opposition in Geneva.
The event was first mentioned by President Vladimir Putin last month who said he believed that militants in Syria would soon be defeated.
Russia again avoided UN involvement in Syria when they dismissed a report by a UN-led panel that blamed the Syrian regime for a sarin gas attack on the rebel-held town of Khan Sheikhoun as "superficial and unprofessional".
"We believe that the report turned out to be superficial, unprofessional and amateurish," said the foreign ministry's security and disarmament department head, Mikhail Ulyanov. "The mission did their research from a distance, that in itself is a scandal."
In their 14th report since 2011, UN investigators said they had in all documented 33 chemical weapons attacks to date.
Twenty-seven were by the government of President Bashar Al Assad, whom Moscow supports.
Russian forces are fighting alongside Syrian government troops against armed rebels and other opponents. Moscow says it's fighting a war on terrorism.