Gold traded slightly lower on Friday, heading for a weekly loss of about 1 percent, as festering uncertainty over the outlook for the global economy dragged on prices. Spot gold edged down 0.1 percent to $1,713.19 an ounce by 0750 GMT, on track for a weekly loss of 1 percent, after prices climbed more than 3 percent the prior week. US gold was little changed at $1,713.60.