WASHINGTON, Jan 25 (Reuters) - Boeing CEO Dave Calhoun "offered no assurance" that the planemaker would withdraw its request for an exemption that would allow its 737MAX 7 jet to be certified without meeting certain regulations, U.S. Senator Tammy Duckworth said in a posting on X following a Thursday meeting with Calhoun. (Reporting by Valerie Insinna; Editing by Leslie Adler)