Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. US Military 'Impressed' by Cooperation with Turkey in Syria; Erdogan Issues Warning Dorian Jones ISTANBUL - Senior U.S. military officers claim "impressive" progress in cooperation with NATO ally Turkey in northeast Syria. But Turkish President Recep Tayyip Erdogan is warning of unilateral action against Washington's critical Syrian ally if Turkish security demands aren't met by the end of the month. "I am constantly impressed by what the CJOC [Combined Joint Operation Center] has achieved in such a short period of time," said Brig. Gen. Christian Wortman in a briefing to journalists. "I would like to compliment our Turkish allies for their high levels of professionalism." CJOC is based in Turkey's Sanliurfa province, which borders Syria. The command center was set up under an August agreement between U.S. and Turkish generals to create what Washington calls a "security mechanism," and what Ankara refers to a "safe zone," in northeast Syria. .