UPDATE 2-Gundlach says flatter Treasury yield curve could become a concern

NEW YORK, June 21 (Reuters) - The U.S. Treasury yield curve flattening could become a concern for economic growth when two-year and three-year Treasury note yields are about the same, and the price per barrel of WTI crude oil falls into the $30-dollar range, said Jeffrey Gundlach, chief executive at DoubleLine Capital, on Wednesday.