Turkey will launch an operation east of the Euphrates in northern Syria against the U.S.-backed Kurdish YPG militia, Turkish President Recep Tayyip Erdoğan said on Sunday.

“We entered Afrin, Jarabulus and Al-Bab. We will go into the east of the Euphrates next,” Erdoğan said, referring to areas captured by Turkish-backed Syrian rebels.

Erdoğan has threatened to enter Syria for the past year-and-a-half, but was thwarted by the United States, which proposed establishing a 19-mile “safe zone” along the border in December.

However, Turkey has accused the United States of stalling on setting up the zone and has demanded it sever relations with the YPG, which Ankara sees as a terrorist organization. Turkish officials have said any such “safe zone” should be under Turkish control, with all YPG elements removed from the region.

“We have told Russia and America this,” Erdoğan said during a televised speech, “because for as long as we are subject to harassment, it is not possible for us to stay silent. We can only be patient for so long. That patience will come to an end.”

According to Turkey, Turkish soldiers have come under fire from YPG forces, which Ankara has called a “terrorist offshoot” of the Kurdish movement within Turkey that has been fighting for independence since 1984.

The Kurds are Turkey’s largest minority, comprising 15 percent to 20 percent of the population. However, Kurds and Kurdish culture have been targeted by the controlling regimes over the decades, with the Kurdish language, dress, culture and even names being banned at various times due to political tensions.

Reports by local media indicate that Turkish military and commando units have been sent to border towns on the Syrian border over the past few weeks.