Russia announced a 48-hour cease-fire in Aleppo late Wednesday, hours after the United States called for for Russia and Syrian President Bashar al-Assad to respect a nationwide truce agreed upon in February.
"On Russia's initiative, a 'regime of silence' has been introduced in Aleppo for 48 hours from 00:01 16 June (2101 GMT Wednesday) with the goal of lowering the level of armed violence and stabilizing the situation," the Russian defense ministry said in a statement.
U.S. Secretary of State John Kerry is accusing Russia and the Syrian government of selectively enforcing the cease-fire, while Assad’s forces continue their campaign to retake Aleppo, the largest city in the country and a UNESCO world heritage site.
"It is very clear that the cessation of hostilities is frayed and at risk and that it is critical for a genuine cessation to be put in place,” Kerry said Wednesday in Oslo, Norway.
He added, "Russia needs to understand that our patience is not infinite, in fact it is very limited with whether or not Assad is going to be held accountable."
"So we have made it very clear, that unless we get a better definition of how this cessation is going to work, how it will be enforced, who is applies to, how it is applied, we are not going to sit there while Assad continues to offensively assault in Aleppo and while Russia continues to support in that effort," he said.
Kerry said members of the Syrian opposition will also be held accountable for the continuance of fighting.
Cease-fire has largely collapsed
The February cease-fire has largely collapsed and little progress is being made to negotiate a political transition that is supposed to begin on August 1.
Syria's civil war has claimed more than 280,000 lives and has forced millions to seek refuge, mainly in Europe. The fighting started with the repression of anti-government protests in March 2011.
Kerry visited Norway for the annual Oslo Forum meeting that convenes senior conflict mediators and high-level decision-makers, as well as analysts and experts to share their experiences, identify challenges and reflect on mediation practice.
Kerry also met Iranian Foreign Minister Mohammad Javad Zarif for talks on Syria and the Iran nuclear deal.
The Oslo Forum is co-hosted by the Royal Norwegian Ministry of Foreign Affairs and the Center for Humanitarian Dialogue, a Switzerland-based private diplomacy organization.