MEXICO CITY, May 18 (Reuters) - U.S. officials have asked Mexico to review whether workers at a Panasonic auto parts factory were denied collective bargaining and freedom of association rights, the U.S. Trade Representative said on Wednesday, marking the third U.S. labor complaint under a new trade deal.

The request comes after a Mexican union last month petitioned U.S. labor officials to probe alleged worker rights abuses at Panasonic's plant in the northern border city of Reynosa. (Reporting by Daina Beth Solomon Editing by Chris Reese)