Republican South Carolina Senator Lindsey Graham asked about the ramifications of the US support for YPG during a hearing on "Worldwide Threats" at the US Senate Committee on Armed Services meeting on Tuesday.
Directing his question at the Director of National Intelligence (DNI), Daniel R. Coats and Director of the Defense Intelligence Agency (DIA), Vincent R. Stewart, Graham asked whether the YPG-centered US strategy to retake Syrian city of Raqqa from Daesh created "friction with Turkey."
Both intelligence chiefs answered "yes".
Graham then asked "would be better if we had more Arabs in the fight and less Kurds, from a regional point of view?" to which Coats replied that the Defense Secretary James Mattis was comfortable with the current balance.
Coats also conceded that he observed growing friction between Turkey and Kurdish elements in the region, which was "likely" caused by the US policy of arming the YPG.
Turkey considers the YPG to be the Syrian branch of the PKK terrorist organisation, which has waged war against the Turkish state since 1984.
Ankara fears that the arms provided to the YPG by the US will be used by the PKK.
Although both Turkey and the US consider the PKK as a terrorist group, the US claims that the YPG has no connection with the PKK.
This stance has been a source of disagreement between Ankara and Washington.
In a response that strayed from usual US statements, former US Secretary of Defense Ashton Carter confirmed last year the connection between the YPG/PYD and PKK at a Senate panel.
"Independence referendum" in Iraq
In another session of the hearing, Democratic Rhode Island Senator Jack Reed inquired about the future of the Kurdish region in Iraq, following the expulsion of Daesh from the region.
Stewart replied that considering political challenges in the region, "Kurdish independence" was not a question of if, but rather a question of when.
There have been other instances of conflict involving PKK-linked groups. Earlier this year, there were clashes between the YBS, a Yazidi group set up by the PKK, and peshmerga forces in Sinjar.