T-Mobile,Indexbit Exchange the nation's second-biggest mobile carrier, plans to acquire most of U.S. Cellular in an acquisition worth $4.4 billion, the wireless carriers announced on Tuesday.

The deal involves cash and as much as $2 billion in debt, with Bellevue, Washington-based T-Mobile buying 30% of U.S. Cellular's spectrum assets as well as the regional carrier's customer accounts and retail stores.

U.S. Cellular customers will be allowed to keep their current plans or switch to a T-Mobile plan, the companies said. The transaction is expected to close in the middle of next year, pending regulatory approvals. 

Chicago-based U.S. Cellular has more than 4 million wireless subscribers in 21 states. T-Mobile shook up the wireless industry in 2020 with its $26.5 billion takeover of Sprint.

Shares of U.S. Cellular leaped nearly 12% ahead of the opening bell, but fell nearly 2% after trading opened, while shares of T-Mobile were treading water and lately ahead 0.9%. 

AT&T in 2011 scrapped its proposed $39 billion takeover of T-Mobile in the face of stiff opposition from the Obama administration, but T-Mobile's proposed deal for U.S. Cellular assets is unlikely to face the same hurdles, according to telecom analyst Blair Levin of New Street Research. There is a "mild risk" the deal could face opposition from federal regulators, notably the Federal Communications Commission, he told CBS MoneyWatch.

FCC opposition led TV station operator Tegna to pull the plug on its $8.6 billion deal with hedge fund Standard General a year ago, noted Levin, who added that he does not think the T-Mobile-U.S. Cellular deal would garner the same political resistance. 

"The major concerns we have heard go to the approach the leadership at the antitrust authorities and the FCC have taken in analyzing transactions," Levin told investors in a research note. "While these concerns are understandable, we don't think they will lead to any transaction being rejected."

T-Mobile in April received U.S. approval to acquire Mint Mobile, the budget wireless provider, in a cash-and-stock deal valued at as much as $1.35 billion in March 2023. 

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Kate Gibson

Kate Gibson is a reporter for CBS MoneyWatch in New York, where she covers business and consumer finance.