US Cellular (USM) said Thursday it agreed to sell some of its spectrum licenses to telecommunications giant AT&T (T) for about $1.02 billion in cash.

The tower operator said the deal is part of its plan to monetize the spectrum that was excluded from its May agreement with T-Mobile US (TMUS). Under the terms of that deal, T-Mobile agreed to acquire US Cellular's wireless operations and select spectrum assets for $4.4 billion. Last month, US Cellular announced deals to sell certain retained spectrum licenses to Verizon Communications (VZ) and two other mobile network operators.

"We are pleased with the significant value that will be realized in the various transactions recently announced," US Cellular Chief Executive Laurent Therivel said in a Thursday statement.

The AT&T deal includes 1.25 billion MHz-Pops of 3.45 GHz and 331 million MHz-Pops of 700 MHz B/C block licenses, US Cellular said. The $1.02 billion deal consideration is subject to potential adjustments.

"The anticipated future deployment of this wireless spectrum will increase AT&T's 5G wireless network capacity in more than 100 markets across virtually every region of the country," an AT&T spokesperson told MT Newswires in an e-mailed statement.

Some of the licenses included in the deal are owned by a third party, US Cellular said. The sale of those assets to AT&T is subject to US Cellular's acquisition of equity in the third party that the company doesn't currently own.

US Cellular 83% shareholder Telephone and Data Systems (TDS) has approved the AT&T deal. Substantially all of the deal is subject to US Cellular closing its transaction with T-Mobile, along with regulatory approvals.

"After our proposed sales, we will be left with 1.86 billion MHz-Pops of low- and mid-band spectrum, as well as 17.2 billion MHz-Pops of mmWave spectrum, with the substantial majority of retained value in the C-band spectrum," Therivel said. "We will continue to look for ways to opportunistically monetize the C-band, as well as the other remaining spectrum."