Maria Zakharova said at a news conference that Lavrov will travel later in the day to meet Kerry in Hamburg, a day earlier than expected.
Kerry said that he hopes to convince Syria's warring factions and their backers to return to the negotiating table before the besieged Syrian city of Aleppo is destroyed.
Russia is a key backer of Syrian President Bashar Assad.
Lavrov complained yesterday that talks with Washington are not working and that the rebels would be wiped out if they don't leave eastern Aleppo.