WASHINGTON (Reuters) - The U.S. Defense Department said on Wednesday it had awarded a $646 million contract to a construction company to design and build a replacement for the border wall in Arizona. In a statement, the Pentagon said the work by Albuquerque, New Mexico-based Southwest Valley Constructors was expected to be completed by Jan. 31, 2020. The work will be performed in the Tucson sector, which includes most of the Arizona border with Mexico. The Pentagon did not indicate the length of the wall to be built.