What last week was just a not-so-thinly-veiled-threat lobbed by John Kerry to the Kremlin has, now that Russia suspended its participation in a Plutonium cleanup accord with the US, become official, and as the State Department announced moments ago, the US has now suspended bilateral discussions, i.e. diplomatic relations, with Russia over Syria, escalating the conflict in the war-torn nation to a level last seen in late 2015.

"This is not a decision that was taken lightly," State Department spokesman John Kirby said, cited by AFP, accusing Russia and its Syrian ally of stepping up attacks on civilian areas. Kirby said the Russian and US militaries will continue to use a communications channel set up to ensure their forces do not get in each others' way during "counterterrorism operations in Syria."

Kirby's full statement is below:

The United States is calling home personnel who had been sent to Geneva in order to set-up a "Joint Implementation Center" with Russian officers to plan coordinated strikes.

And US diplomats will suspend discussions with Russia on reviving a September 9 deal reached between US Secretary of State John Kerry and Russia's Foreign Minister Sergei Lavrov. Under that protocol, a truce came into effect on September 12 but it collapsed within a week amid bitter recriminations and a surge of fighting in the five-year-old civil war.

Washington has accused Moscow of failing to rein in President Bashar al-Assad's government forces and abetting his strikes on civilian targets. Moscow, meanwhile, says the United States failed to separate "moderate" anti-Assad rebels from Al Qaeda-linked jihadists.

"Unfortunately, Russia failed to live up to its own commitments, including its obligations under international humanitarian law," Kirby said, in the statement.

According to the US spokesman, Russia was "either unwilling or unable to ensure Syrian regime adherence to the arrangements to which Moscow agreed.

"Rather, Russia and the Syrian regime have chosen to pursue a military course, inconsistent with the Cessation of Hostilities, as demonstrated by their intensified attacks against civilian areas." Kirby accused Moscow and Damascus of "targeting of critical infrastructure such as hospitals, and preventing humanitarian aid from reaching civilians in need."

Kirby repeated Washington's charge that Russia and the regime were responsible for the deadly September 19 attack on a United Nations aid convoy in northern Syria, outside Aleppo. He had nothing to say about the confirmed US-alliance strike on Syrian troops that killed over 60 soldiers.

While we await the Russian response, we can't help but note that the drums of (global, non-proxy) war in Syria are beating ever louder. The next escalatory step from the US at this point would be to send US troops in Syria, which would be promptly met with a matched retaliatory response by Russia, and perhaps China too, which as reported several weeks ago, informally joined the conflict on the side of Syria's president Assad when it said it would provide "aid and military training" to Syria's current president.