A senior State Department envoy has written a highly critical assessment of the Trump administration's abrupt withdrawal of troops from northeast Syria, warning of war crimes and ethnic cleansing as a consequence.
Two officials familiar with the matter said the internal memo by William Roebuck, the top American diplomat in northern Syria, takes the administration to task for not doing enough to prevent Turkey's invasion of the region and protect US-allied Kurdish fighters there.
Turkey invaded days after President Donald Trump ordered the small number of US special forces in the area to leave, ostensibly so they would not be caught in a crossfire between the Turks and Kurds.
One of the officials described the memo, which was obtained and first revealed by The New York Times, as "lengthy and harsh", but the pair were not authorised to discuss internal documents publicly and spoke on condition of anonymity.
In the memo quoted by the Times, Roebuck said there was no way to know if more pressure on Turkey's president, Recep Tayyip Erdogan, would have stopped the operation.
"It's a tough call, and the answer is probably not. But we won't know because we didn't try," the Times quoted Roebuck as writing.
Roebuck, a top deputy to the US special envoy for Syria, James Jeffrey, said the withdrawal had badly, if not irreparably, damaged the trust of the Kurds, who have been fighting the Islamic State group alongside US forces.
He also raised concerns about the possibility that Turkish-backed militias taking part in the operation were undisciplined and could commit atrocities amounting to war crimes. Such allegations have already been made.
"Turkey's military operation in northern Syria, spearheaded by armed Islamist groups on its payroll, represents an intentioned-laced effort at ethnic cleansing," Roebuck was quoted as writing.
He said such abuses "can only be described as war crimes and ethnic cleansing".
The State Department declined to confirm or deny the existence of the memo, but offered a long statement defending the administration's actions that tacitly admitted there is robust internal debate on Syria policy.
"This administration's job is to do what is best for US national security and the American people," spokeswoman Morgan Ortagus said.
"That is what we have done in Syria and what we will continue to do."