The State Department on Monday announced that it was following through on a threat to cut off talks on Syria with Russia following a marked increase in Russian and Syrian bombing of the city of Aleppo.
"This is not a decision that was taken lightly," State Department spokesman John Kirby said in a statement.
Russia, he added, was "either unwilling or unable to ensure Syrian regime adherence to the arrangements to which Moscow agreed" as shown through the continued bombing of hospitals and other civilian infrastructure in Aleppo.
Kirby also said that the US would be withdrawing personnel it had meant to deploy to a joint US-Russia coordination cell, but would continue to work with Russia to deconflict missions the Russians carried out in Syria with those the US-led coalition launches.
State Department spokeswoman Elizabeth Trudeau elaborated during the department's daily press briefing that Russian and US officials met throughout the weekend to attempt to avoid following through on the threat to the cooperation with Russia over Syria that Secretary of State John Kerry issued last Wednesday. The final decision to cut off talks was made today, she added.
Russia has denied accusations that it has targeted hospitals and other humanitarian missions, including the attack on a UN-Syrian Arab Red Crescent convoy that left at least 20 people dead.
"Accusations that Russia is allegedly attacking medical facilities, hospitals and schools are ... baseless," Russian Deputy Foreign Minister Gennady Gatilov said at a news conference on Monday.
Upon learning of the suspension, Russia quickly attempted to shift the blame for the collapse of the deal the two countries brokered in early September back to the United States.
"Washington simply failed to fulfill a key condition of the agreement for relieving the humanitarian situation for Aleppo residents," Russian foreign ministry spokewoman Maria Zakharova said on state-owned Channel 1, referring to a requirement that US-backed rebels withdraw from a contested area in Aleppo. "And now, apparently, having failed to fulfil these agreements, which they drew up themselves, are trying to shift the blame to someone else," she said, noting that Russia "regret[s] Washington's decision."
The Duma, Russia's parliament, may respond to the US action by ratifying a deal with Syria granting Russia a permanent presence in the country, the BBC reported. Russia's bombing campaign to shore up the government of Russian ally Syrian President Bashar al-Assad was only meant to last a few months, but it entered its second year last week.
The escalation also comes on the same day that Russian President Vladimir Putin declared that his country was suspending a deal with the US over disposing of plutonium from nuclear weapons. While not tied to Syria, the suspension hits on several of the sticking points the US and Russia have been grappling with for the past two years, including US and European sanctions against Russia for its invasion of Ukraine in 2014. The end of those sanctions, Putin said, would be required before the plutonium deal could resume.