The deal, which was announced last December, included the acquisition of wireless spectrum by Verizon from the four companies, Comcast, Time Warner Cable, Bright House Networks and Cox Communications. At the same time, Verizon and the cable companies agreed to resell each other's services and work together on research of future technologies.

On Thursday, the DOJ said it would allow the spectrum portion of the deal to go ahead, but won't let the resale and research part go forward without changes.

The spectrum deal involves Verizon purchasing unused wireless space held by the four cable companies. Verizon will use some of the spectrum for its own services, sell some to T-Mobile under a June 2012 agreement, and auction the remaining spectrum.

This wireless space, a finite resource, is vitally important for Verizon and T-Mobile because it directly affects the speed, reach and strength of wireless service that can be offered to consumers. The cable companies bought the spectrum in 2006 as part of a high-profile public auction, but most of it went unused.

On the second part of the deal, the Justice Department found the deal would harm competition because Verizon's FiOS fiber-to-the-home Internet service competes with the cable companies in many markets.