The UN Security Council is scrambling to reach agreement on a resolution seeking a cease-fire in Syria and has put back a vote until February 24.
The vote on a motion calling for a 30-day truce in Syria to allow for the delivery of humanitarian aid and to evacuate wounded civilians has already been postponed several times since February 22.
U.S. President Donald Trump on February 23 accused Russia, Iran, and the Syrian government of being responsible for a "humanitarian disgrace" in Syria.
"I will say what Russia and what Iran and what Syria have done recently is a humanitarian disgrace," Trump told a news conference at the White House.
"What those three countries have done to those people is a disgrace," he added.
Russia has previously voiced opposition to the resolution, saying it is unrealistic and that it ignores the fact that many Islamic State (IS) fighters remain in the region.
French President Macron and German Chancellor Angela Merkel appealed to Russian President Vladimir Putin to back the resolution and to press its Syrian government ally to stop the bombardments of a rebel-held enclave outside Damascus.
Witnesses reported a new wave of bombs hit the enclave in Syria's eastern Ghouta district on February 23. More than 400 civilians reportedly have been killed in the district since February 18.
"The massacre in Eastern Ghouta must stop now," EU foreign policy chief Federica Mogherini said in a statement. "The European Union is running out of words to describe the horror being experienced by the people of Eastern Ghouta."
Turkish Foreign Minister Mevlut Cavusoglu said earlier on February 23 that "Russia and Iran must stop the regime."
He also said that the bombardment of Eastern Gouta and a government offensive against rebel-held positions in Idlib Province was "contrary" to agreements negotiated in Astana by diplomats from Ankara, Moscow, and Tehran.
Earlier, the United States criticized Russia over the bombing of Eastern Ghouta, saying Moscow has a "unique responsibility" for the deaths of hundreds of civilians there during the past week.
The U.S. State Department called on Russia to use its influence over the Syrian government to stop the killing while U.S. diplomats pushed for passage of the Security Council resolution.
State Department Spokeswoman Heather Nauert blamed Russia for not curbing Syrian President Bashar al-Assad and his army, which launched an all-out campaign in February to defeat militants in Eastern Ghouta.
"What are they doing to stop the devastation, the deaths, the murders that are taking place in Syria?" Nauert asked journalists in Washington. "Without Russia backing Syria, the devastation and the deaths would certainly not be occurring."
"It is a good reminder that Russia bears a unique responsibility for what is taking place there," she said.
Nauert also blamed Moscow for what she called "throwing a wrench" into negotiations at the UN over the resolution to establish a temporary cease-fire.
Russia's UN ambassador rejected the Western-drafted resolution, raising the possibility of a veto when the council votes.
Ambassador Vasily Nebenzya said the media and Western nations are conducting a "misinformation campaign" about the fighting in Ghouta and are ignoring what he called the "inconvenient truth" that several thousand fighters from a group affiliated with Al-Qaeda reside there.
Nauert said the fighting in Ghouta shows the failure of Russian-sponsored peace negotiations over Syria, known as the Astana process, which designated Eastern Ghouta as a "de-escalation zone" where fighting was supposed to be on the decline.
"It shows what a farce this de-escalation zone has become," Nauert said.
At the United Nations, U.S. ambassador for economic and social affairs Kelley Currie said Assad is trying to "bomb or starve" his enemies into submission in Ghouta, just as he did in Aleppo, Hama, and Homs.
She said Assad is counting on Russia to provide the cover he needs at the UN so his forces can "keep bombing and gassing these 400,000 people" who live in Ghouta.
The Syrian army on February 22 dropped leaflets calling on Ghouta residents to leave for their own safety and urging opposition fighters to hand themselves over. The leaflets were similar to those dropped over rebel-held neighborhoods during the government's siege of Aleppo.
Syrian UN Ambassador Bashar al-Ja'afari told the UN Security Council that Ghouta will be the "second Aleppo."
With reporting by AP, AFP, and Reuters