Russia hosted Syrian and Iranian delegations for separate rounds of talks on Monday in a renewed diplomatic push for a Syrian peace conference in which Moscow says Tehran must also play a role.
President Vladimir Putin, who has stepped up his personal involvement on the Syrian issue, also called Iran's president to discuss the conflict as well as efforts to end the dispute over Tehran's nuclear programme.
Moscow wants to show it still has weight in the Middle East and has been emboldened by its success in helping to broker a deal under which Syria will destroy its chemical weapons, but Washington is wary of allowing Iran to join Syrian peace talks.
"We regard Iran as a very important partner in all Middle Eastern affairs," Interfax news agency quoted Russian Deputy Foreign Minister Mikhail Bogdanov saying at the start of talks with Iran's Deputy Foreign Minister Hossein Amir-Abdollahian.
The meeting "will give us an opportunity to jointly look at how developments in and around Syria unfold," Bogdanov said.
Russia, which strongly backs Syrian President Bashar al-Assad, and the United States announced back in May they would try to organise a peace conference bringing Syria's government and opposition together, but a date has so far proved elusive.
Russian Foreign Minister Sergei Lavrov was quoted on Monday as saying it could happen before the end of the year.
"(U.S. Secretary of State John) Kerry and I promised to do all we can to make that happen," Lavrov told Rossiiskaya Gazeta, referring to a telephone conversation the two men had on Sunday.
But Lavrov added that the timing of the conference would "depend on how well our Western partners do their homework of persuading the opposition to reject preconditions".
A Syrian government delegation led by Deputy Foreign Minister Faisal Mekdad was also in Moscow for talks, though despite earlier local media reports, there was no sign of a delegation from Syria's main opposition, the National Coalition.
There was no immediate word on how Russia's talks with the Iranian or the Syrian delegations had gone.
In his telephone conversation with Iran's President Hassan Rouhani, Putin "noted the importance of efforts that have been taken to organise the 'Geneva 2' conference," the Kremlin said.
Russia has been Assad's most powerful backer in the conflict, sending arms and blocking Western efforts to condemn his government or increase pressure on it by imposing sanctions.
Moscow says it is not trying to prop up Assad but that his exit from power cannot be a precondition for a peace process.
Syria's National Coalition agreed last week to attend peace talks but said there could be no future role for Assad in Syria.