"We will be having consultations in the trilateral format -- Russia, the United States and the UN," Deputy Foreign Minister Gennady Gatilov told RIA Novosti state news agency today.
UN peace envoy Staffan de Mistura is set to take part in the talks aimed at ending a brutal war that has killed more than 250,000 people and forced millions from their homes since March 2011.
Gatilov said Russia would be calling for the "intensification of joint efforts" in the "fight against terrorism".
Kerry said he would visit Moscow next week as Russia and the United States work to forge a framework for a Syrian ceasefire and political transition.
Moscow has sought, so far without success, to persuade nations in the US-led coalition that opposes Assad to work with its own forces flying a bombing campaign in Syria and with Damascus in a broader coalition against the Islamic State (IS) group.
It was the first time a broad range of Syrian political and armed opposition factions have come together since the conflict erupted.
But another Russian deputy foreign minister, Mikhail Bogdanov, deplored that Ahrar al-Sham -- which is linked to Al-Qaeda's Syrian affiliate Al-Nusra -- and the rebel Jaish al-Islam (Army of Islam), had been invited to the Riyadh talks as they are "strongly suspected of being terrorist organisations".
