Russia bears responsibility for Saturday night's chemical attack in Eastern Ghouta, due to its "unwavering support" for the Syrian regime, the US State Department said in a statement.
It comes after a deadly chemical attack in the last rebel stronghold of Eastern Ghouta killed up to 100 civilians, with the US blaming Bashar al-Assad's regime and its backers.
"The Assad regime and its backers must be held accountable and any further attacks prevented immediately," said State Department Spokesperson Heather Nauert.
"Russia, with its unwavering support for the regime, ultimately bears responsibility for these brutal attacks, targeting countless civilians, and the suffocation of Syria's most vulnerable communities with chemical weapons."
Russia has been a stalwart diplomatic backer of the Syrian regime since the start of the war.
In September 2015, it entered the war and launched air strikes on Syrian opposition areas, helping the regime turn back a series of defeats to rebel forces.
Russia has been widely criticised for allegedly targeting civilian areas, including homes, hospitals, schools and markets.
Despite this, Moscow has put itself forward as a "guarantor" for so-called "de-escalation zones" in Syria.
Eastern Ghouta, which has been subject to weeks of horrendous bombing and now it appears a chemical attack, was supposed to be covered by these ceasefire zones.
Russia is suspected of playing a key role in airstrikes on the area, which has left hundreds dead.
"The United States calls on Russia to end this unmitigated support immediately and work with the international community to prevent further barbaric chemical attacks," the statement ended.
Activists said scores have been killed in the chemical attack that targeted Douma, the last area of Eastern Ghouta still under rebel control.
Photos from the scene showed whole families dead and foaming from their mouths in what analysts are saying points to the use of deadly sarin.
Douma was subject to huge air raids and chlorine attacks in the hours before the chemical attack, which the US says targeted a hospital.
Russia and the Syrian regime have both denied involvement in the attack, but it comes one year after another major use of sarin in the opposition village of Khan Sheikhoun.
Eastern Ghouta was subject to another sarin attack in 2013, which killed hundreds of civilians.
Washington said it has no doubt who is responsible for the latest chemical attack.
"The United States continues to use all efforts available to hold those who use chemical weapons, in Syria and otherwise, accountable. The regime's history of using chemical weapons against its own people is not in dispute."
The US launched cruise missile strikes on a Syrian regime airbase in response to the 4 April 2017 chemical attack on Khan Sheikhoun.
The Syrian regime narrowly avoided similar strikes after the 2013 Eastern Ghouta killings, when it agreed to hand over its chemical weapons stockpiles. Countless chlorine - and at least two sarin - attacks have continued.
This article has been adapted from its original source.
Copyright @ 2019 The New Arab.