The U.S. government could move to block the proposed $26.5 billion merger of T-Mobile (TMUS) - Get Report and Sprint (S) - Get Report , the third and fourth largest telecom carriers in the country, as soon as next week, CNBC reported. 

The Justice Department's antitrust division could sue to block the deal next week if it cannot reach a settlement on the assets the companies will have to divest to meet antitrust concerns. 

Future control of pay-television operator Dish Network is reportedly one of the sticking points holding off regulatory approval. CNBC also reported, however, that optimism remains that a settlement is possible.