US President Donald Trump imposed sanctions on Turkey over Ankara's military operation in northeast Syria, and called for an immediate ceasefire.
Turkey launched the cross-border assault on Kurdish fighters last Wednesday after Trump withdrew some US troops from the region, drawing sharp criticism from fellow Republicans who accused him of abandoning allies who had fought against Islamic State of Iraq and the Levant.
Trump said he would send Vice President Mike Pence and national security adviser Robert O'Brien to Ankara as soon as possible in an attempt to begin negotiations.
Pence said Trump had spoken directly to Turkey's president Recep Tayyip Erdogan, who promised not attack the border town of Kobane.
"President Trump communicated to him very clearly that the United States of America wants Turkey to stop the invasion, implement an immediate ceasefire and to begin to negotiate with Kurdish forces in Syria to bring an end to the violence," Pence said.
The sanctions apply to individuals, entities or associates of the Turkish government involved in "actions that endanger civilians or lead to the further deterioration of peace, security and stability in northeast Syria", US Secretary of State Mike Pompeo said in a statement.