WASHINGTON (Reuters) - U.S. Defense Secretary Jim Mattis on Wednesday slammed what he said were  absolutely false  media reports asserting that President Donald Trump had called for an increase in the U.S. nuclear arsenal.  This kind of erroneous reporting is irresponsible,  Mattis said in a written statement. NBC had reported that Trump sought a tenfold increase in the U.S. nuclear arsenal, something Trump had already denied. 