Turkish President Recep Tayyip Erdogan said on Sunday that Turkish military forces will enter the eastern part of the Euphrates river in Syria.
"We entered Afrin, Jarablus, al-Bab. Now we will enter the east of the Euphrates," Erdogan said at an event in the northwestern city of Bursa.
The Turkish leader said Turkey had shared this information with the United States and Russia.
"As long as the harassment fires continue, we cannot remain silent," Erdogan said, adding "We have been running out of patience."
The Turkish military and its allied Syrian rebels grabbed al-Bab, Jarablus and Afrin from the Islamic State and the Syrian Kurdish militia respectively in past two operations.
A US military delegation is scheduled to arrive in the Turkish capital on Sunday for a new round of talks, as past negotiations failed to produce an agreement on jointly creating a safe zone in the northern part of Syria controlled by the Kurdish militia, the People's Protection Units (YPG), which is seen by Turkey as a terror group.
Ankara has long threatened another military offensive east of the Euphrates in Syria to wipe out the US-backed YPG forces, and has reinforced forces along the YPG-controlled part of the border amid differences with Washington over the security zone.
Turkey will move to establish the safe zone on its own in case the talks with the US fail, Turkey's Foreign Ministry spokesman Hami Aksoy said on Friday.
"If the safe zone is not established as planned and threats against our country continue, we will launch the military operation in the east of the Euphrates," Turkish Foreign Minister Mevlut Cavusoglu said earlier.
Turkey is also annoyed that not much progress has been made on a joint plan with the US on clearing the YPG militants from the northern Syrian town of Manbij.
Ankara and Washington, two NATO allies, agreed to work together on a safe zone in the YPG-controlled part of Syria early this year after the White House announced a troop withdrawal from Syria and President Erdogan put off a threatened operation east of Euphrates in Syria.