After repeated air raids on rebel-held parts of Aleppo, including hospitals, Washington says it has abandoned its effort to convince Russia to impose a ceasefire in Syria.
Declaring it had run out of patience with Moscow, the White House accused the Kremlin of failing to live up to its commitments under a ceasefire deal.
It also blamed Russia for helping the Syrian government intensify attacks on civilians.
“Everybody’s patience with Russia has run out. They’ve also spent a great deal of credibility in making a series of commitments without any clear indication that they were committed to following them,” White House spokesman Josh Earnest said.
In response, Russia’s foreign ministry said it regretted the US’ decision. Accusing the White House of trying to shift responsibility for the failure to stop the violence, spokeswoman Maria Zakharova also said Washington had failed to improve the humanitarian conditions around Aleppo.
Hundreds of civilians, including children, are thought to have been killed in Aleppo since government forces launched a major offensive to take full control of the city after the ceasefire broke down.