The US$39 billion acquisition would create a "Twin Bell duopoly," giving AT&T and Verizon Communications a combined 82 percent of the mobile market in the country, Sprint said Tuesday. Approval of the acquisition would take the U.S. mobile market back to the 1980s, when only two carriers had mobile licenses in each area, Sprint said in .

The FCC's spectrum auctions in the 1990s "gave rise to Sprint, T-Mobile, and other wireless carriers, and ushered in an era of competition and growth that has greatly benefitted consumers," Sprint's representatives wrote. "Wireless competition has sparked a technological revolution in broadband data services, applications and devices. The proposed transaction would turn back the clock on competition and innovation and bring this era of unprecedented wireless expansion and technological innovation to an abrupt, but avoidable, halt."

Sprint has opposed the deal since the companies announced it in March. The deal would merge the second largest mobile carrier in the U.S. with the fourth largest, creating a new leader.

AT&T has argued that it needs T-Mobile's spectrum to keep up with growing demand for mobile broadband service. Sprint disputed that argument, saying AT&T already controls the most spectrum of any U.S. mobile carrier. AT&T is the "industry laggard" in deploying next-generation mobile broadband, a source close to Sprint said Tuesday.

AT&T noted that "dozens" of groups, including labor unions, politicians and community and minority groups, have voiced support for the deal. "We anticipate additional support for the transaction from more voices who recognize the tremendous benefits for the economy, innovation and public policy associated with bringing high-speed wireless broadband deployment to more than 97 percent of the U.S. population -- nearly 55 million more Americans than our pre-merger plans -- and improving call quality and network performance for consumers," an AT&T spokeswoman said.