US Threatens Russia Over Syria as UN Decries 'Slaughterhouse' John Kerry decries Russian and Syrian attacks, says US will cut off all contact By Newser Editors and Wire Services Posted Sep 28, 2016 11:27 AM CDT 55 comments Comments A Civil Defense worker carries the body of a child after airstrikes hit al-Shaar neighborhood in Aleppo, Syria, on Tuesday. (Syrian Civil Defense White Helmets via AP)A Civil Defense worker carries the body of a child after airstrikes hit al-Shaar neighborhood in Aleppo, Syria, on Tuesday. (Syrian Civil Defense White Helmets via AP) (Newser) – Secretary of State John Kerry is threatening to cut off all contact with Moscow over Syria, unless Russian and Syrian government attacks on Aleppo end, the AP reports. The State Department says Kerry issued the ultimatum in a Wednesday telephone call to Russian Foreign Minister Sergey Lavrov. Kerry's spokesperson, John Kirby, says Kerry expressed grave concern over Russian and Syrian government attacks on hospitals, water supplies, and other civilian infrastructure in Aleppo. He says Kerry told Lavrov the US holds Russia responsible for the use of incendiary and bunker-buster bombs in an urban area. Kerry told Lavrov the US was preparing to "suspend US-Russia bilateral engagement on Syria," including on a proposed counterterrorism partnership, "unless Russia takes immediate steps to end the assault on Aleppo" and restore a ceasefire. UN chief Ban Ki-moon says the situation in rebel-held parts of Aleppo is worse than a "slaughterhouse" and implicitly accuses Syria and Russia of committing war crimes, the AP reports. Without naming countries, Ban said Wednesday that "those using ever more destructive weapons know exactly what they are doing—they know they are committing war crimes." The Syrian government announced the offensive to retake rebel-held eastern Aleppo, and the only countries carrying out airstrikes are Syria and Russia. Ban said "hospitals, clinics, ambulances, and medical staff in Aleppo are under attack around the clock." "International law is clear," he said. "Medical workers, facilities and transport must be protected. The wounded and sick, civilians and fighters alike, must be spared. Deliberate attacks on hospitals are war crimes."