Defense Secretary Mark Esper said Sunday that Turkey "appears to be" committing war crimes in its incursion into northern Syria.

"It appears to be, if true, that they would be war crimes," Esper agreed on CBS's "Face the Nation" on Sunday when host Margaret Brennan described some of Turkey's actions against Kurdish forces as war crimes, including footage appearing to show the summary execution of Kurdish captives.

"It's a very terrible situation over there, a situation caused by the Turks, by President [Recep Tayyip] Erdoğan. Despite our opposition, they decided to make this incursion," Esper said.

Esper also said officials need to sort out reports that Turkish forces attacked U.S. Special Forces in Syria.

"We've given them the locations of our forces. But look, I've been to war. I know what war's like. There's a fog out there, and things happen," he said.

He also confirmed that about 1,000 U.S. troops would be withdrawn from northern Syria as part of a "deliberate withdrawal." The Defense secretary, however, pushed back when Brennan asked if the U.S. withdrawing from northern Syria and turning over operations to Turkey was "a retreat," telling the host, "I wouldn't characterize it this way. ... We did not want to put American forces into harm's way."

"Turkey committed this action. They decide to make an incursion in northern Syria despite our protestations, our urgings not to do it, all of our warnings," Esper added. "We are doing what's in the interests of our service members not to put them in harm's way."

Esper also struck a different note from other members of the Trump administration on the House's ongoing impeachment inquiry, telling Brennan that Pentagon officials "will do everything we can to comply" with recent subpoenas from House Democrats.

This report was updated at 10:36 a.m.