Nov 7 (Reuters) - United States Cellular ( USM ) said on

Thursday it has agreed to sell a portion of spectrum licenses

used to transmit mobile phone signals and high-speed data

services to AT&T ( T ) in a $1.02 billion deal.

The transaction is part of the regional wireless carrier's

strategy to monetize its spectrum assets that were not part of

the previously announced sale to T-Mobile.

In May, U.S. Cellular entered into an agreement with

T-Mobile to sell almost all of its wireless operations including

customers, stores and 30% of its spectrum assets in a deal

valued at $4.4 billion.

Last month, U.S. Cellular agreed to sell select spectrum

licenses for $1 billion to Verizon. It also signed deals with

two other mobile network operators, but did not disclose the

details.

The latest agreement "adds a fourth mobile network operator,

in addition to T-Mobile, to the list of those whose subscribers

will benefit from the sale of our spectrum licenses," U.S.

Cellular CEO Laurent Therivel said on Thursday.

Including the proposed T-Mobile transaction, U.S. Cellular

has reached agreements to monetize about 70% of its total

spectrum holdings, excluding high-frequency mmWave spectrum, the

company said in a statement.