President Barack Obama declared Friday that Bashar al-Assad's Syrian regime, Iran and Russia are responsible for the carnage in Aleppo and argued there was nothing Washington could have done to stop the war, short of a military takeover of Syria.
And he warned Assad, who has been engaged in a brutal civil war against opposition forces since 2011, that he will not be able to "slaughter his way to legitimacy."
"The world as we speak is united in horror at the savage assault by the Syrian regime and its Russian and Iranian allies on the city of Aleppo," he told an end-of-year news conference.
"This blood and these atrocities are on their hands," he said.
Obama also admitted to reporters that he had asked himself whether the United States did enough to halt the conflict.
"There are places around the world where horrible things are happening and - because of my office, because I'm president of the United States - I feel responsible," he said. "Is there something I could do that would save lives and make a difference and spare some child who doesn't deserve to suffer?"
But the president said there had been no public appetite for the kind of large-scale US military intervention earlier in the war that he believes would have been the only way to halt it. READ MORE