Turkey
Reports
[U.S.-Turkish joint patrols to oversee security in the northern Syrian city of Manbij could probably start soon after Washington and Ankara agreed on a plan for the withdrawal of Kurdish fighters.] Decisions on vetting and personnel changes in security/governance structures will undoubtedly take longer — that is where implementation challenges could arise.
The greatest threat from the U.S. perspective is direct military conflict between Turkish and American forces...Erdogan seems determined to force the Americans to fulfill past promises that YPG forces would return east of the Euphrates. The challenge for the US is whether that promise can be kept while also maintaining order on the ground.