This is true and was said during a press conference held by President Biden. Live coverage of the press conference by NBC News shows President Biden stating, "including enhancing our radar to pick up more slow-moving objects above our country" (18:30-18:37). The press conference was held to address the Chinese balloons that have been observed and shot down by the United States. Through increasing the radar, NORAD (North American Aerospace Defense Command) was able to "track 3 unidentified objects, one in Alaska, Canada, and over Lake Huron" (18:40-18:45).
(34) LIVE: Biden delivers remarks on unidentified aerial objects | NBC News - YouTube