The delegation, headed by diplomat Max Martin, met with PKK/PYD commander Aldar Xelil and senior members Fevze Yusuf and Bedran Ciya Kurd during the visit on Friday, local sources told Anadolu Agency.
The U.S. officials were briefed about the terrorist group's demands for the set-up of a federal system in Syria, the sources said, speaking on condition of anonymity due to restrictions over talking to the media.
The delegation also visited the northern city of Ayn al-Arab (Kobani) and held talks with Sahin Cilo, the commander of the U.S.-backed SDF that is largely controlled and manned by the PKK/PYD.
They later met with members of the Raqqah provincial council, which was founded by the PKK/PYD to give the impression that the city was being run by a civil administration.
There was no comment from the U.S. State Department on the report.
Cilo is one of the main PKK/PYD commanders and has been supervising the group's military operations in northern Syria in coordination with U.S. officials.
Talal Silo, a defected SDF spokesman who has fled to Turkey, earlier told Anadolu Agency that Cilo and the U.S. administration were in "full coordination".
The PKK/PYD is the Syrian affiliate of the PKK, which has waged a terror campaign against Turkey for more than 30 years, leading to the deaths of more than 40,000 people.
The PKK -- listed as a terrorist organization by the U.S. and EU as well as Turkey -- resumed its armed campaign in July 2015. Since then, it has killed more than 1,200 Turkish security personnel and civilians, including women and children.