The combined company would bring cable or Internet service to about 30% of American subscribers and serve 19 of the country’s 20 largest metropolitan regions.
That would give Comcast, which is already the nation’s largest TV, Internet and home phone provider, an even more sizable lead on its rivals.
The Obama administration will weigh whether that could translate into higher prices, worse service and fewer TV channels for customers.
Comcast and Time Warner Cable will have to gain approval from two regulators: both the Federal Communications Commission and either the Department of Justice or the Federal Trade Commission.
The agencies have not yet decided which will take up the case.
(The FTC typically scrutinizes cable mergers but the DOJ usually handles media deals, including Comcast’s 2010 purchase of NBCUniversal from GE.
The companies said in a statement the deal will be “pro-competitive” and “strongly in the public interest.”
For instance, Comcast noted that it has higher broadband Internet speeds than Time Warner Cable, more high-definition offerings, and the deal will help make future broadband and digital TV deployment cheaper for the combined company.
Comcast and Time Warner Cable also said that they barely compete, since there is little overlap between their customer markets. Satellite TV companies Dish and DirecTV as well as Verizon FiOS and AT&T’s U-verse will still compete with the combined company in many of those regions.
Comcast has also offered to divest 3 million customers to competitors, giving the combined company 30 million subscribers. That compares to 20.2 million DirecTV customers in the U.S., 14 million who subscribe to Dish and 5 million AT&T U-verse and Verizon FiOS customers, according to the National Cable and Telecommunications Association.