"This unacceptable incursion has also undermined the successful multinational 'Defeat ISIS' mission in Syria, and resulted in the release of many dangerous ISIS detainees," Esper said in a statement.

Esper said he would travel to NATO headquarters in Brussels next week to ask allies "to take collective and individual diplomatic and economic measures in response to these egregious Turkish actions."

Esper condemned the decision last week by Recep Tayyip Erdogan, president of NATO member Turkey, to launch an assault on the Kurdish militia in northeast Syria as "unnecessary and impulsive," saying the result was widespread casualties, refugees and insecurity.

On Sunday he announced the withdrawal of nearly 1,000 US troops from the area because of the threat to them from the fighting.

"President Erdogan bears full responsibility for its consequences, to include a potential ISIS resurgence, possible war crimes, and a growing humanitarian crisis," he said.