Angela Lang/CNET

After the US Federal Communications Commission voted to approve T-Mobile's $26.5 billion merger with Sprint on Oct. 16, the approval has now become official. The FCC found the new T-Mobile will "help close the digital divide and advance United States leadership in 5G." But it wasn't a unanimous vote -- FCC Commissioner Jessica Rosenworcel issued a 17-page dissenting opinion after last month writing in The Atlantic about voting against the deal.

"T-Mobile and Sprint have committed within three years to deploy 5G service to cover 97% of the American people, and within six years to reach 99% of all Americans," the FCC said Tuesday. "This commitment includes deploying 5G service to cover 85% of rural Americans within three years and 90% of rural Americans within six years."

FCC Chairman Ajit Pai's recommendation in August was to approve the merger, but the FCC said Wednesday its approval is on the condition these commitments are fulfilled. It added the new T-Mobile will provide 90% of Americans with 100Mbps mobile speeds within six years, and 99% with 50Mbps. The carrier's compliance will be checked by the FCC and an independent third party.

If they fail to comply within six years, T-Mobile could be fined up to $2 billion.

The merger will also "enhance competition in rural America," the FCC said.

On the other side of the fence, Rosenworcel argued Tuesday that it will reduce competition.

"Three companies will control 99% of the wireless market. By any metric, this transaction will raise prices, lower quality, and slow innovation," she wrote. Shrinking the number of national providers from four to three will hurt consumers, harm competition, and eliminate thousands of jobs."

The FCC and Justice Department have been "wooed" by T-Mobile's "unenforceable concessions and hollow promises," she added.

T-Mobile CEO John Legere said the merger would bring 5G to all.

"New T-Mobile officially has FCC regulatory approval! Thanks to the @FCC for diligent review & for seeing the benefits of #NewTMobile! Some more work to do, but we're so excited for what we'll bring to America! #5GForAll," Legere tweeted Tuesday.

In July, the Justice Department approved T-Mobile's $26.5 billion bid to merge with Sprint, after the deal was OK'd by Pai in May on the condition that T-Mobile and Sprint divested Boost Mobile and satisfied other requirements, including building out 5G in rural areas and offering wireless home broadband good enough to substitute for fixed line service.

However, the deal is still facing opposition from 17 state attorneys general. The state of New York is leading the charge, but the lawsuit now includes New York, California, Colorado, Connecticut, Hawaii, Maryland, Massachusetts, Michigan, Minnesota, Nevada, Texas, Illinois, Virginia, Wisconsin, Oregon, the District of Columbia and Pennsylvania.

Mississippi has since exited the suit, however, with Attorney General Jim Hood in October reaching an agreement with T-Mobile. Under the deal, the carrier will deploy a 5G network that provides 100Mbps speeds to 62% of the state's urban and rural population; cover 92% of the population and 88% of its rural population within six years of merging; and "limited price commitments."

T-Mobile said previously that it wouldn't proceed with closing the deal until it settles the concerns of the state attorneys general.

"Consumers should hope these state officials succeed," Rosenworcel said Tuesday. "Count me among them."

Democratic presidential candidate Senator Elizabeth Warren also took issue with the merger, citing competition issues.

"The @FCC's final approval of the T-Mobile/Sprint merger officially hands control of nearly 100% of wireless services to 3 corporate giants – strangling competition & harming consumers, workers, & small businesses," Warren tweeted Wednesday.

First published at 11:28 a.m. PT on Oct. 16.

Updated at 1:48 p.m.: Adds statement from T-Mobile; Mississippi has exited the lawsuit; Nov. 5 at 12:33 p.m.: Adds FCC, Rosenworcel and Legere comments from November; Nov. 6 at 2:31 p.m.: Adds comment from Warren.