The Pentagon revealed it would be keeping troops in Syria after the defeat of the Islamic State Militant group, in spite of calls from the country and it's Russian and Iranian allies to expel US forces, whose presence they consider illegal. The intention is to support US partners and prevent the return of terrorist groups.
The US also wants to create conditions so that refugees may return safely and create a Syria free of weapons of mass destruction. The US also has the motive to resolve the conflict between the Syrian regime and people and work toward a Syrian led alternative to Assad's rule and the Iranian presence. The US aims to help provide stability and facilitate peace in the Middle East.