But they do have an incentive to pretend. Taking a lesson from North Viet Nam.
Just give the US some face saving way out and then unleash their own brand of Hell.
Of course they are also expert in drawing US concessions in return for the US being allowed some face saving.
A loss loss (in the bargain and in the result)for the US and Israel.
I don't think Syria and Iran could stop the slide into chaos even if they wanted to. Syria isn't run by Sunnis in any event (Assad is an Alawaite, which is some Shia sect), so it is not like each side has a sponsor. So if the face saving exit strategy is to create some temporary reduction in the violence, while the US leaves, I doubt that will happen, and there will be no saving of face.