A Russian official has said for the first time that the Syrian government may be defeated by opposition forces.
President Bashar al-Assad's forces are "losing more and more control and territory", deputy foreign minister Mikhail Bogdanov said.
He said Russia, one of Syria's staunchest allies, was making plans for a possible evacuation of thousands of its citizens.
Separately, Syria denied reports it had fired Scud missiles at rebels.
Nato's Secretary General Anders Fogh Rasmussen earlier said the organisation had detected the launch of such short-range missiles, saying it showed an "utter disregard" for the lives of the Syrian people.
Russia, along with China, has used its veto at the UN Security Council to block resolutions condemning the Syrian government's use of violence.
But Mr Bogdanov said on Thursday: "Unfortunately, we cannot rule out the victory of the Syrian opposition."
Mr Bogdanov repeated Russia's call for dialogue between the two sides, predicting that the fighting would grow more intense.
He said tens, possibly hundreds of thousands of people would be killed if that happened.
"If such a price for ousting the president seems acceptable to you, then what can we do? We consider it unacceptable," he said.
Mr Bogdanov said plans were being drawn up for a possible evacuation of Russian citizens.
"We have mobilisation plans and are clarifying where our citizens are located," he said.
Mr Bogdanov also raised concerns about "extremists" seizing chemical weapons arsenals, according to the Interfax news agency.
Western nations have in recent days raised the prospect of Syrian government forces themselves using chemical weapons.
Mr Bogdanov's comments do not mean Moscow has changed its official position, the BBC's Steve Rosenberg in Moscow reports.
Russia still maintains that the ousting of President Assad would deepen the conflict, but this is the first time Russia has publicly acknowledged that the Syrian president faces possible defeat, our correspondent adds.
In Brussels, Mr Rasmussen said the collapse of the Syrian government was "only a question of time", adding that President Assad should "initiate a process to accommodate the legitimate aspirations of the Syrian people".
Speaking in Jordan, a minister in the Iraqi government, Rafa al-Essawi, also said that "Syrian changes will take place shortly", telling AFP news agency: "I think, personally, it is weeks."
At a meeting in Morocco on Wednesday, more than 100 countries recognised an opposition coalition as the sole "legitimate representative" of the Syrian people.
A day earlier, the US had recognised the National Coalition, drawing a sharp response from Russian Foreign Minister Sergei Lavrov, who said Washington had decided to place all its bets on the coalition achieving an "armed victory".
On Thursday, US state department spokeswoman Victoria Nuland said that Washington wanted "to commend the Russian government for finally waking up to the reality and acknowledging that the regime's days are numbered".
In Syria itself, state-run news agency Sana reported a blast in the Damascus suburb of Qatana which it said killed 16 people, including seven children.
The state TV channel al-Ikhbariya later said a second bomb attack, in Jdaidet Artuz, close to Damascus, had killed eight people, most of them women and children.
Violence has been increasing in and around the capital in recent weeks as rebels try to close in on the city.
The Local Coordination Committees in Syria, the umbrella organisation of local Syrian groups opposed to the government, said "Syrians are closer to victory than ever before".
It said in a statement that the "Battle for Damascus" was approaching the heart of the capital.
It urged the Free Syrian Army and residents to protect property and places of worship, and preserve documents and records that "contain massive amounts of incriminating evidence... and will be required to hold the regime accountable".
Government forces have been mounting severe bombardments of areas with a rebel presence.
On Wednesday, US media quoted American officials as saying "Scud-type missiles" had been fired at rebels.
Nato confirmed short-range missiles had been launched, with Mr Rasmussen saying: "It is reckless and I strongly condemn it."
An army defector still in contact with his old brigade told AFP he had been informed that five missiles were fired north-westwards from army positions on the road between Damascus and Homs three days ago.
Syria on Thursday denied it had fired such weapons.
"The foreign ministry confirms that these missiles were not used in confronting the terrorist groups," a ministry statement carried by Sana said.
"Scuds are strategic, long-range missiles and are not suited for use against armed terrorist gangs," the ministry said.