NEW YORK(TheStreet) - Verizon's $3.6 billion December purchase of wireless spectrum from a joint venture held by Comcast, Time Warner Cable and Bright House Networks may face an antitrust challenge by the U.S. Department of Justice, according to reports from Bloomberg citing unnamed sources. If a formal challenge were to emerge, it would cast a pall over Verizon's move to bolster its mobile phone services to handle growing smartphone data demands a day after competitor AT&T withdrew from a $39 billion purchase of T-Mobile on antitrust grounds. Along with the spectrum acquisitions, Verizon and the cable companies involved in the spectrum deal committed to marketing agreements between each other to sell their respective mobile phone and "Triple Play" cable packages.