U.S. officials in a Senate panel in the U.S. congress in April admitted that there were links between the PKK and the Democratic Union Party (PYD) and its armed-wing, the People's Protection Units (YPG).

Secretary of Defense Ashton Carter had answered in the affirmative when asked by Sen. Lindsey Graham whether the PYD and the YPG, are aligned with the PKK terrorist organization.

Admitting the link between the PKK and PYD, Carter acknowledged that the PKK is a designated terrorist group by the U.S. and Turkey but denied Ankara is upset by U.S. air and equipment support to the militant group's offshoot in Syria.

Sen. Graham told him that he was recently in Turkey and the government there was not happy with U.S. support for a terror group.

"They think this is the dumbest idea in the world and I agree with them," Graham said.

He said that Ankara has been asked by Washington to do more in the fight against DAESH. Graham also said he does not believe the Turkish government's argument is "absurd."

"If you are wondering why Turkey is a little upset, we are arming people inside Syria who are aligned with a terrorist group. That is the finding of the Turkish government," he said.

The U.S. has long claimed that the PYD is not a terrorist organization. Washington also refused to acknowledge the link between the two terrorist organizations. U.S. State Department spokesman John Kirby said in March that the U.S. does not consider the PYD or the YPG to be terrorist organizations.