This is
their statement - the bolded bit suggest they are offering to join the regime assault on Idlib in return - presumably from the north to complete encirclement:
“The self-administration of northern and eastern Syria, through its military forces, the Syrian Democratic Forces formed out of all the components of the Syrian self-management areas, fought terrorism starting from Kobani in 2014 and then continued the battles of liberation against this terrorist group in northern and eastern Syria, as it managed to liberate Manbij west of the Euphrates, Tal Abyad, Tabqa until it reached the alleged capital of ISIS “al-Raqqa” and then to Deir ez-Zor and declared victory over this group after five years of fighting on March 23, 2019.
This liberated geographical area is equivalent to one third of the total territories of Syria. The SDF lost 11 thousand martyrs and 24 thousand wounded, including permanent disabilities during these battles.
This was a high price to liberate the Syrians and all the components from the oppression and brutality of these terrorist organizations and to preserve the territorial integrity of Syria.
Our political project in northern and eastern Syria did not call for secession, but we have been calling for dialogue and resolving the Syrian crisis peacefully. We did not attack any country, especially Turkey, though it persists to call us terrorists while it played an important role in supporting terrorism in Syria. Today, Turkey is invading the Syrian territory liberated by the SDF with the blood and sacrifices of its children.
During the past five days, the most heinous crimes against unarmed civilians have been committed. The SDF has responded with dignity and courage resulting in the death and injury of its fighters, in order to save the Syrian integrity, however Turkey is continuing its assault. As a result, we had to deal with the Syrian government that has the duty of protecting the country's borders and preserve Syrian sovereignty, so that the Syrian army can enter and deploy along the Syrian-Turkish border to support the SDF to repel this aggression and liberate the areas entered by the Turkish army and its hired mercenaries.
This agreement offers an opportunity to liberate the rest of the Syrian territories and cities occupied by the Turkish army as Afrin and other Syrian cities and towns.
Therefore, we call on all our people and all components in northern and eastern Syria, especially the border areas, that this deployment came through coordination and compatibility with the self-administration of the North and East Syria and the Syrian Democratic Forces.”