The talks between Syrian National Coalition chief Ahmad Jarba and Foreign Minister Sergei Lavrov came after an inconclusive 10-day peace conference in Geneva broke up on Friday without a firm commitment from Damascus to attend a new round set for February 10.
The so-called Geneva II talks were promoted jointly by Washington -- a firm backer of the Syrian opposition -- and Moscow -- an ally of the Damascus regime -- in a bid to convince the warring sides to sit down for direct negotiations for the first time.
But Syrian President Bashar al-Assad's team and the opposition made no progress on local ceasefires or permission for humanitarian corridors to some of the country's more devastated cities such as Homs.
Russia's Deputy Foreign Minister Gennady Gatilov told the state-run RIA Novosti news on Tuesday that "we expected the government delegation, as it had previously assured us, to take part in future negotiations with the opposition."
Yet Gatilov also conceded that "for now, it is premature to talk about any decisions (about a new round of talks) because these have not yet been made."
A Jarba aide said the umbrella opposition group was especially concerned that Syrian Foreign Minister Walid Muallem had avoided any discussion of a transitional government that could pave the way for Assad's removal from power.
"The main subjects of discussion with the Russian foreign minister will be the delivery of humanitarian assistance to Syrian cities, the release of prisoners from Syrian jails, and the formation of a transitional government," Jarba's head adviser Monzer Aqbiq told RIA Novosti.
"Considering this last point, we have many questions that we will be able to discuss with Moscow," Aqbiq was quoted as saying.
Russia had earlier invited Jarba to Moscow for a visit on the eve of the Geneva conference that would have coincided with a trip by representatives from Assad's government.
Jarba's staff said prior commitments had prevented him from flying to Moscow at the time.
The opposition chief had earlier said that Lavrov had told him that the Kremlin's position on the role of Assad was not set in stone.
But Moscow has sided with its traditional Middle East ally in public and said that Assad's departure from power should not be a precondition for political change.
Russia has also insisted that the negotiations should first and foremost focus on fighting the rapid spread of Islamic extremist groups in Syria -- a position promoted by Assad but treated with suspicion by the opposition.
"The regime wants to talk about humanitarian assistance and avoid a discussion of political issues," Syrian National Coalition secretary general Badr Jamous told the Interfax news agency.
Russia and the opposition's Western and Arab allies have clashed not only over the future role of Assad but also the makeup of the negotiations teams.
Lavrov has repeatedly argued that the talks should be joined by Iran -- a condition rejected by the rebels because of the Islamic republic's close connections to the Assad regime.
But a Russian diplomatic source told Moscow's Kommersant daily that Washington has proposed a compromise that would allow Iran along with Saudi Arabia and Turkey -- two ardent foes of Assad -- to join a separate set of negotiations that would be conducted alongside the Geneva talks.
Kommersant said that US Secretary of State John Kerry had forwarded the proposal to Lavrov during their talks on the sidelines of the weekend Munich Security Conference.
"The Russian side, according to Kommersant sources, broadly approved this idea," the newspaper wrote.