Some 40 Syrian opposition groups yesterday rejected Russia's proposed peace talks in Sochi, accusing Moscow of failing to pressure its ally, Bashar Assad, to end the conflict.

In a series of statements, the groups, including some of Syria's most prominent, as well as political opposition umbrella groups, said the talks expected next month are an attempt to "circumvent" the U.N.-led process, which has made virtually no progress since it began in 2014.

They said Moscow has asked them to give up their demand for Assad to step down. "We reject this, and we affirm that Russia is an aggressor that has committed war crimes against Syrians," the statement signed by the groups said. "Russia has not contributed with a single move to alleviate the suffering of the Syrian people and it has not pressured the regime it claims it guarantees to move an inch toward any real path toward a resolution."

The opposition groups, including Ahrar al-Sham, Army of Islam, and a number of Free Syrian Army (FSA) groups, said they are committed to the U.N.-led Geneva process, and called on the international community to end the bloodshed, now in its seventh year. Political opposition groups and governing bodies in opposition-held areas have also rejected Russia's proposed talks.

"Russia is an aggressor country that has committed war crimes against Syrians [...] It stood with the regime militarily and defended its politically and over seven years preventing U.N. condemnation of Assad's regime," the statement added.

Moscow says it targets militants but the opposition and residents say the Russian airstrikes conducted since a major aerial campaign over two years ago has caused hundreds of civilian casualties in indiscriminate bombing of civilian areas away from the frontline. Some opposition groups have not yet made up their mind.

U.N. Syria envoy Staffan de Mistura said that Russia's plan to convene the congress should be assessed by its ability to contribute to and support the U.N.-led Geneva talks on ending the war in Syria.

Russia's deputy foreign minister said yesterday that the Syrian National Dialogue Congress, planned to be convened in Russia, "should take place under the auspices of the United Nations."

Speaking to RIA Novosti news agency, Mikhail Bogdanov said all steps toward resolving the Syrian crisis had been taken in line with U.N. Security Council resolution 2254.

Bogdanov urged all parties involved in the Syrian crisis to respect the sovereignty and territorial integrity of the country.