US Secretary of State John Kerry called his Russian counterpart on Wednesday and warned him that Washington will end talks on the Syrian conflict unless Moscow halts the assault on Aleppo.
A State Department spokesman said Kerry told Foreign Minister Sergei Lavrov that plans to set up a joint US-Russia military cell to target jihadist groups in Syria would also be put on hold.
"He informed the foreign minister that the United States is making preparations to suspend US-Russia bilateral engagement on Syria... unless Russia takes immediate steps to end the assault on Aleppo and restore the cessation of hostilities," spokesman John Kirby said.
Kerry and Lavrov have been leading international efforts to bring Syria's five-year-old civil war to an end, and on September 9 agreed to demand a ceasefire.
Moscow was to order its ally Syrian leader Bashar al-Assad to rein in his military and end the bombardment of civilian communities, and Washington was to persuade rebel forces to separate themselves from the jihadist Fateh al-Sham, the former Al-Qaeda affiliate once known as Al-Nusra Front.
But fighting continued and the truce collapsed.
The US-led coalition bombed a Syrian military base, saying later that it had been targeted in error by warplanes hunting the Islamic State group. READ MORE