"The deployment of tanks and artillery in Aleppo neighbourhoods, the bombing and displacement of unarmed civilians, and attempts to storm Kurdish neighbourhoods during the negotiation process undermine the chances of reaching understandings," Abdi said in a statement.

Abdi, who leads the US-backed, Kurdish-led Syrian Democratic Forces (SDF), visited Damascus on Sunday for talks on implementing the March deal, but state media said the discussions failed to produce tangible results.