U.S. President Barack Obama has strongly condemned the "barbarous Russian and Syrian regime airstrikes" on civilians in eastern Aleppo.
The White House says Obama spoke by telephone Thursday with German Chancellor Angela Merkel. Both agreed that Russia and the Assad regime bear a "special responsibility" for stopping the fighting and letting humanitarian aid get in.
Secretary of State John Kerry said earlier the U.S. is "on the verge" of suspending diplomatic talks with Russia because of Moscow's continued bombing of rebels in eastern Aleppo.
A monitoring group said Friday Russian airstrikes across the country in the past year have killed more than 9,000 people, including many civilians. The Britain-based Syrian Observatory for Human Rights said many more civilians were wounded by the airstrikes.
In Aleppo itself, hundreds of thousands of civilians are stuck in the city. Half of them are children.
Kerry called it “irrational” to keep talking and “take things seriously” after the Russians vowed to continue the airstrikes.
“It’s one of those moments where we’re going to have to pursue other alternatives for a period of time,” said Kerry. He added he is “extremely concerned” about the future of the Syrian people.
Kerry's spokesman told reporters the State Department is in "active" contact with the Kremlin, but are still prepared to step away "barring some significant steps by Russia."
"We are still prepared to enact that kind of a suspension and we're in consultations right now inside our own government, and of course, with Foreign Minister Lavrov,” John Kirby said Thursday.
Washington has pressed Moscow to use its influence to pressure Bashar al-Assad to honor a cessation of hostilities agreement and allow the flow of humanitarian aid to Aleppo and around Syria.
Instead, U.S. officials say the Syrian and Russian governments have intensified their air attacks on Aleppo, targeting hospitals, refugee camps, water supplies and other critical sites.
"There has been a shameful strategy implemented by the Assad regime, and aided and abetted by the Russians, to try to bomb civilians into submission," said White House press secretary Josh Earnest.
Accusations against Russia
U.S. strategy in Syria has focused on degrading and destroying Islamic State. The Obama administration said that while progress has been made in pushing back the terrorist group, more must be done to secure a sustained cease-fire and political transition to end the five-year civil war.
The United States and European Union are accusing Moscow of quashing diplomatic efforts to halt the fighting, a claim Russia has rejected.
German Chancellor Angela Merkel and Turkish President Recep Tayyip Erdogan said Russia has a "special responsibility to calm violence and give a political process a chance" in Syria.
Kremlin spokesman Dmitry Peskov insisted Moscow still wants to reach a deal to renew the Sept. 9 deal on a cessation of fighting. But, he said, "We have unfortunately taken note of the rather unconstructive character of the rhetoric from Washington over the past few days."
U.N. humanitarian aid chief Stephen O'Brien told the Security Council Thursday that what is happening in Aleppo fills him with "raw grief, dismay, intense sadness, frustration and an unquenchable anger."
"Besiegement is not a weapon of war. It is a flagrant, unjustifiable breach of the law. One day there will be no hiding place for the individuals and institutions callously, cynically perpetrating these war crimes."
O'Brien also had harsh words for U.N. diplomats for their perceived inaction in Syria.
"The only remaining deterrent it seems is that there will be real accountability in the court of world opinion and disgust. Goodness knows, nothing else seems to be working to stop this deliberate and gratuitous carnage."
Russia said it supports a 48-hour cease-fire in Aleppo, but not a longer truce proposed by the U.S.
The United Nations has described the plight of Aleppo as desperate.
Officials say medical evacuations are needed and food stocks are running low. In a city of about 250,000 people, there are only 14,000 food rations remaining, according to U.N. officials.
Reporter Ken Schwartz, United Nations correspondent Margaret Besheer, State Department correspondent Nike Ching, and reporter Lisa Schlein in Geneva contributed to this report.