The Justice Department on Friday approved the merger of T-Mobile and Sprint, the nation’s third and fourth-largest wireless carriers by subscribers, after the companies agreed to sell assets and help Dish to create a new fourth nationwide carrier.

The deal will require Sprint and T-Mobile to sell some of their wireless spectrum to Dish and will require both Dish and the new combined company to build 5G networks across the U.S.

Makan Delrahim, chief of Justice’s antitrust division, said the agreement establishes Dish as “a disruptive force in wireless.”

“Americans’ access to fast, reliable and affordable wireless connectivity is critically important to our economy and to every American consumer and to their way of life,” Delrahim said in a press conference Friday.

Verizon currently has a 35.5 percent share of the wireless market in the U.S. AT&T has about 33 percent. The combined T-Mobile and Sprint is expected to have around 30 percent, meaning around 95 percent of U.S. wireless customers will be in the hands of three companies.

Sprint and T-Mobile have argued that their combination would allow them sufficient scale to build a 5G network. In the agreement announced Friday, T-Mobile pledged to build a 5G network covering 97% of the U.S. population in three years and not to raise prices during that period.

Dish said Friday that it has reached an agreement with the Federal Communications Commission to build a 5G broadband network covering 70 percent of the U.S. population by June 2023.

The deal still faces challenges from at least 13 state attorneys general, including the attorneys general of New York and California. Critics say that allowing the two companies to combine will dangerously lower competition in wireless communications and harm consumers.