Russia says a Syria ceasefire plan is more likely to fail than succeed, as Syrian government forces backed by Russian air strikes took rebel ground near Aleppo and set their sights on the Islamic State stronghold of Raqqa province.
International divisions over Syria surfaced anew at a Munich conference where Russia rejected French charges it was bombing civilians, just a day after world powers agreed on the "cessation of hostilities" due to begin in a week's time.
US Secretary of State John Kerry on Saturday (local time) 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.
In another sign of escalation, Turkey's military shelled Kurdish militia targets near the northern Syrian town of Azaz on Saturday, a Turkish military source said.
The Syrian army also looked poised 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.
A Syrian military source said the army captured positions at the provincial border between Hama and Raqqa in the last two days and intends to advance further.
"It is an indication of the direction of coming operations towards Raqqa. In general, the Raqqa front is open," the source said.
The cessation of hostilities deal agreed by major powers 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.
Russia has said it will keep bombing Islamic State and the al-Qaida-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.
Assad is showing no appetite for a negotiated ceasefire. He said this week that the government's goal was to recapture all of Syria.
Syrian state television announced the army and allied militia had on Saturday captured the village of al-Tamura overlooking rebel terrain northwest of Aleppo.
Gulf states that want Assad gone from power have said they would be willing to send in troops as part of any US-led ground attack against Islamic State. US Defence 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.
Speaking at the same conference, French Prime Minister Manuel Valls called on Russia to stop bombing civilians in Syria.
"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.