The following is attributable on the record to John Kirby, Spokesperson:
Secretary Kerry spoke this morning via phone with Russian Foreign Minister Sergey Lavrov.
Secretary Kerry expressed grave concern over the deteriorating situation in Syria, particularly for continued? Russian and Syrian regime attacks on hospitals, the water supply network, and other civilian infrastructure in Aleppo. The Secretary made clear the United States and its partners hold Russia responsible for this situation, including the use of incendiary and bunker buster bombs in an urban environment, a drastic escalation that puts civilians at great risk.
The Secretary stressed that the burden remains on Russia to stop this assault and allow humanitarian access to Aleppo and other areas in need. He informed the Foreign Minister that the United States is making preparations to suspend U.S.-Russia bilateral engagement on Syria – including on the establishment of the Joint Implementation Center – unless Russia takes immediate steps to end the assault on Aleppo and restore the cessation of hostilities.
Source: U.S. State Department