By Alexandra Alper and Karen Freifeld Reuters (Adds quote from hearing, background, attempt to get company comment) WASHINGTON, Sept 21 (Reuters) – U.S. President Joe Biden's nominee to a post overseeing export policy on China said on Tuesday he sees Chinese telecoms firm Huawei as a national security threat and expects to keep the company on a trade blacklist unless "things change." If confirmed as Under Secretary of Commerce for Industry And Security, former Pentagon official Alan Estevez also pledged to "look at" China's Honor – a handset unit spun off of Huawei – to see whether the telecommunications company…