Russian Deputy Foreign Minister Sergei Ryabkov said on Monday that Moscow and Washington are still divided over Tehran's participation in the conference slated for June.
Nevertheless, the Russian Foreign Ministry believes that the event would not be successful if Iran were not invited, Ryabkov said.
The Russians and Americans agreed during US Secretary of State John Kerry's visit to Moscow to set up a conference of international players to end the crisis in Syria. Moscow wants to involve all the nations which took part in the Geneva conference on Syria last summer, and says without Iran's participation the conference cannot succeed.
Late in May, Russia's Foreign Minister Sergei Lavrov underlined that Iran should take part in the upcoming Geneva II Conference.
"This issue is not related to the Syrians alone, as there are a number of foreign players involved at that crisis as well, and therefore, Iran's presence at that conference is of key importance for us," Lavrov said.
"In my talks with the US and French foreign ministers John Kerry and Lauran Fabio aimed at solving the ambiguities about the combination of participating countries at Geneva II International Conference on Syria I gained their approval on need for revising their former decision," he added.
Also in May, Iranian Foreign Ministry Spokesman Seyed Abbas Araqchi announced that Tehran is likely to take part in the Geneva II Conference on Syria if the co-hosts, the US and Russia, invite it to the international gathering.
"If the Geneva II Conference is held and if Iran is invited, we will study our presence with a positive view," Araqchi said at the time.