\Russia said on Saturday a ceasefire deal for Syria agreed by major powers was more likely to fail than succeed, as Syrian government forces backed by further Russian air strikes gained more ground against rebels near Aleppo.
International divisions over Syria surfaced anew at a Munich conference where Russia rejected French charges that it was bombing civilians, just a day after world powers agreed on the "cessation of hostilities" due to begin in a week's time.
U.S. Secretary of State John Kerry reiterated accusations that Russia was hitting "legitimate opposition groups" and civilians with its bombing campaign in Syria and said Moscow must change its targets to respect the ceasefire deal.
The conflict, reshaped by Russia's intervention last September, has gone into an even higher gear since the United Nations sought to revive peace talks. These were suspended earlier this month in Geneva before they got off the ground.
The Syrian army looked poised on Saturday to advance into the Islamic State-held province of Raqqa for the first time since 2014, apparently to pre-empt any move by Saudi Arabia to send ground forces into Syria to fight the jihadist insurgents.
The cessation of hostilities deal falls short of a formal ceasefire, since it was not signed by the warring parties - the government and rebels seeking to topple President Bashar al-Assad in a five-year-old war that has killed 250,000 people.
If its forces retake Aleppo and seal the Turkish border, Damascus would deal a crushing blow to the insurgents who were on the march until Russia intervened, shoring up Assad's rule and paving the way to the current reversal of rebel fortunes.
Russia has said it will keep bombing Islamic State and the al Qaeda-linked Nusra Front, which in many areas of western Syria fights government forces in close proximity to insurgents deemed moderates by Western states.
Russian Foreign Minister Sergei Lavrov, asked at a security conference in Munich on Saturday to assess the chances of the cessation of hostilities deal succeeding, replied: "49 percent."
Asked the same question, his German counterpart Frank-Walter Steinmeier put the odds at 51 percent.
The complex, multi-sided civil war in Syria, raging since 2011, has drawn in most regional and global powers, caused the world's worst humanitarian emergency and attracted recruits to Islamist militancy from around the world.
Assad, backed on the ground by Iranian combatants and Lebanon's Hezbollah in addition to big power ally Russia, is showing no appetite for a negotiated ceasefire. He declared this week that the government's goal was to recapture all of Syria, though he said this could take time.
The U.S. government said Assad was "deluded" if he thought there was a military solution to the conflict.
Syrian state television announced the army and allied militia had on Saturday captured the village of al-Tamura overlooking rebel terrain northwest of Aleppo.
The Syrian Observatory for Human Rights reported advances in the same area, adding that Russian jets had hit three rebel-held towns near the Turkish border.
Government offensives around Aleppo have sent tens of thousands of people fleeing toward the Turkish border.
Advance on Islamic State's Raqqa bastion
The Observatory said government troops had also edged to within a few kilometers (miles) of the provincial boundary of Raqqa after making a rapid advance eastwards along a desert highway from Ithriya in the last few days.
The Syrian government has had no serious foothold in Raqqa province since Islamic State captured Tabqa air base in 2014. "They are on the provincial borders of Raqqa," Observatory director Rami Abdulrahman told Reuters.
Islamic State, driven by the goal of expanding its "caliphate" rather than reforming Syria - the original goal of the opposition when the conflict began as an unarmed street uprising in 2011 - is being targeted in separate campaigns by a U.S.-led alliance and Assad's government with Russian air support. Regional Kurdish forces supported by Washington are also fighting Islamic State in Raqqa province.
Gulf states that want Assad gone from power have said they would be willing to send in troops as part of any U.S.-led ground attack against Islamic State. U.S. Defense Secretary Ash Carter said on Friday he expected Saudi Arabia and the United Arab Emirates to send commandos to help recapture Raqqa.
In what may have been a response to those remarks, Russian Prime Minister Dmitry Medvedev said on Saturday in Munich there was no need to scare anyone with a ground operation in Syria.
Russian, French PMs clash
Speaking at the same conference, French Prime Minister Manuel Valls called on Russia to stop bombing civilians in Syria, saying this was crucial to achieving peace there.
"France respects Russia and its interests ... But we know that to find the path to peace again, the Russian bombing of civilians has to stop," Valls said.
Medvedev said that was simply not true.
"There is no evidence of our bombing civilians, even though everyone is accusing us of this," he said. "Russia is not trying to achieve some secret goals in Syria. We are simply trying to protect our national interests," he said, adding that Moscow wanted to prevent Islamist militants getting to Russia.
Russia also has a major air base and large naval installation on Syria's Mediterranean coast.
Kerry, however, accused Russia of dropping so-called "dumb bombs" in Syria that do not have a precise target, saying this has led to the killing of civilians.
"To date, the vast majority of Russia's attacks have been against legitimate opposition groups. To adhere to the (ceasefire) agreement it made, Russia's targeting must change," Kerry told the Munich conference.
Two Syrian rebel commanders told Reuters on Friday insurgents had been sent "excellent quantities" of Grad rockets with a range of 20 km (12 miles) by foreign backers in recent days to help confront the Russian-backed offensive in Aleppo.
Foreign opponents of Assad including Saudi Arabia and Turkey have been supplying vetted rebel groups with weapons via a Turkey-based operations center.
Some of these groups have received military training overseen by the U.S. Central Intelligence Agency. The vetted groups have been a regular target of the Russian air strikes.