WASHINGTON (Reuters) -U.S. factory production unexpectedly increased in August amid a rebound in the output of motor vehicles and some nondurable goods, though tariffs continued to cast a shadow over the manufacturing sector. Trump has defended the duties as necessary to revive a long-declining U.S. industrial base, though economists argue that effort cannot be accomplished in a short period of time, citing high production and labor costs as among the challenges. Motor vehicle and parts production rebounded ...