Turkish President Recep Tayyip Erdogan announced on Monday that his country would soon launch a new military operation in northern Syria to establish a "safe zone" with a depth of 30 km along its border with its southern neighbor.
State Department spokesman Ned Price told reporters on Tuesday that the United States was "deeply concerned" about the announcement.
"We condemn any escalation and support maintaining the current ceasefire lines," he added.
Since 2016, Turkey has launched three military operations in Syria to drive out Syrian Kurdish fighters who allied with the United States in its campaign against the jihadist Islamic State.