(Corrects headline to "Gold flat" instead of "gold up" and first paragraph to say "Gold was flat" instead of "gold rose") * U.S. dollar, bond yields down * Gold headed for 0.5 percent weekly gain * Gold nudges 100-day moving average By Renita D. Young and Peter Hobson NEW YORK/LONDON, May 11 (Reuters) - Gold was flat on Friday, headed for its first weekly gain in four weeks, as the dollar weakened and investors grew a bit less confident about prospects that the Federal Reserve would raise interest rates three more times in 2018. Spot gold was unchanged at $1,321 per ounce by 1:43 p.m. EDT (1743 GMT). During the session it touched its highest since April 25 at $1,325.96, nudging its 100-day moving average of $1,326. It was up 0.5 percent for the week so far. U.S. gold futures for June delivery settled down $1.60, or 0.1 percent, at $1,320.70 per ounce. "Geopolitical risks in the Middle East, a weaker dollar and softer Treasury yields are giving gold a temporary boost," said Walter Pehowich, executive vice president of investment services at Dillon Gage Metals. The dollar fell for a third day on Friday against a basket of currencies. While the 10-year U.S. Treasury yield rose slightly, it remained below 3 percent. Bond market investors remain confident the Fed will hike rates in June, but less sure of prospects for rate hikes in September and December. A weaker dollar makes gold more attractive for investors using other currencies. Fewer U.S. interest rate hikes would lower the opportunity cost of holding non-interest bearing bullion. St. Louis Federal Reserve Bank President James Bullard said aggressive rate increases would risk nipping off U.S. business investment. Gold price consolidation above resistance at the 100-day moving average might be a catalyst for more gains, MKS PAMP trader Tim Brown said. Capital Economics' Simona Gambarini said the likelihood of three more Fed interest rate hikes this year would probably pressure gold prices into ending 2018 at $1,300. Gold is considered a safe asset in uncertain times, but traders said tensions in the Middle East provided limited support now. "Geopolitical concerns are still a concern but investors aren't paying significant attention," Think Markets chief markets analyst Naeem Aslam said. "The dollar story is more prominent." A summit between the United States and North Korea to be held in Singapore eased fears of conflict. Silver was up 0.3 percent at $16.72 an ounce, above its 100-day moving average and nearing its 200-day moving average to $16.84. It was at 2-1/2-week highs, set for a weekly gain of 1.3 percent. Platinum was down 0.4 percent at $920.49 per ounce, having hit its highest since April 25 at $929.10. It was poised for a nearly 2 percent weekly increase. Palladium declined 0.8 percent at $991 per ounce, but earlier hit $1,008.50, a 2-1/2-week high, closing the week more than 2 percent higher. (Additional reporting by Apeksha Nair in Bengaluru Editing by David Gregorio and Louise Ireland)