US President Barack Obama urged Russia on Sunday to halt air strikes targeting “moderate” opposition fighters in Syria in support of regime leader Bashar al Assad.
In recent weeks, Russian bombardments directed at “moderate” rebel groups are helping Syrian regime achieve big victories and regime is close to recapturing Aleppo, the country’s largest city and commercial centre before the civil war.
World powers agreed on Friday to implement a "cessation of hostilities" and immediately accelerate the delivery of humanitarian aid into Syria within a week. However, the deal was not signed by any of the warring parties fighting on the ground.
The Kremlin reported that President Vladimir Putin and Obama had spoken by telephone and both agreed to strengthen cooperation to implement the Munich deal.
However, a Kremlin statement claimed that Russia was dedicated to its campaign against DAESH and "other terrorist organisations."
Moscow also said the cessation does not apply to its air strikes, which have shifted the balance of power towards Syrian regime.
The White House said Obama's discussion with Putin emphasised on the need to accelerate delivery of humanitarian aid to Syria and end to the air strikes.
"In particular, President Obama emphasized the importance now of Russia playing a constructive role by ceasing its air campaign against moderate opposition forces in Syria," the White House said in a statement.
Humanitarian aid threatened
Relief workers said efforts to deliver humanitarian aid were being threatened by the recent bombardments.
"We must ask again, why wait a week for this urgently needed cessation of hostilities?" said Dalia al Awqati, Mercy Corps director of programs for North Syria.
US Senator John McCain said he did not view the deal as a breakthrough. "Let's be clear about what this agreement does. It allows Russia's assault on Aleppo to continue for another week," he said at a security conference in Munich.
"Mr Putin is not interested in being our partner. He wants to shore up the Assad regime," McCain said.
A senior ally of German Chancellor Angela Merkel said Russia had achieved the upper hand in Syria through bombings.
Russia, the main ally of the Syrian regime, began a campaign of air strikes in support of Bashar al Assad’s forces on September 30.
According to the UN figures, at least 260,000 people have been killed and some 4.3 million Syrians have fled the country since the start of the Syrian civil war.