"The United States condemns the ongoing military offensive that the Assad regime, backed by Russia and Iran, is perpetrating against the people of Eastern Ghouta," the White House said in a statement, referring to Syrian President Bashar al-Assad.
Washington also accused Moscow of ignoring a UN Security Council resolution calling for a 30-day cessation of hostilities, saying Russia has killed "innocent civilians under the false auspices of counter terrorism operations."
"This is the same combination of lies and indiscriminate force that Russia and the Syrian regime used to isolate and destroy Aleppo in 2016, where thousands of civilians were killed," it said, referring to Syria's one-time economic hub, which was devastated by the country's civil war.
The White House also called on pro-regime forces to "immediately cease targeting medical infrastructure and civilians" in Eastern Ghouta.
Assad's forces have seized over a quarter of the enclave on Damascus's eastern edges after two weeks of devastating bombardment, according to the Syrian Observatory for Human Rights, a Britain-based monitor.
The advance on the back of air strikes, artillery fire and rocket attacks that are reported to have killed more than 650 civilians, sent hundreds into flight to western parts of the enclave.
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