U.S. President Donald Trump said on Wednesday that the U.S.-backed YPG militants in Syria were selling oil to Iran and Washington was "not thrilled" about it.

Trump said he did not like the fact that the YPG was selling oil to Iran and that they told the militants to stop.

"The Kurds, our partners, are selling oil to Iran. We are not thrilled about that. I'm not happy about it at all," Trump said.

"We want to protect the Kurds, nevertheless, we want to protect the Kurds but I don't want to be in Syria forever," the president said as he told reporters U.S. military would withdraw from Syria "over a period of time."

During a Cabinet meeting at the White House in front of reporters, Trump said he had never discussed a reported four-month timetable for the withdrawal of 2,000 American troops stationed in Syria amid a battle against Daesh militants.

The U.S. has been providing support to the PKK's Syrian affiliate YPG under the pretext of fighting against Daesh, despite outcry from Ankara, who views the terrorist group's presence on its southern border as a grave threat.

After repeated demands for Washington to end its support to the YPG, Ankara signaled that it may launch a major cross-border operation in the area stretching from the Euphrates River to the Iraqi border to clear the terrorist group from its border region.

Previously, Turkey targeted the YPG in two cross-border operations, Operation Euphrates Shield launched in August 2016 and Operation Olive Branch in January 2018, as well as through air and artillery strikes.

In its more than 30-year terror campaign against Turkey, the PKK — listed as a terrorist organization by Turkey, the U.S. and the EU — has been responsible for the deaths of some 40,000 people, including women and children.