WASHINGTON, June 15 (Reuters) - The chair of the Senate

Commerce Committee on Monday questioned a plan from private

investment firm Grain Management to acquire key wireless

spectrum from T-Mobile but potentially delay its use

for years.

Last year, T-Mobile agreed to sell its portfolio of 800 MHz

licenses to private investment firm Grain Management for $2.9

billion in cash and all of Grain's 600 MHz spectrum licenses.

Republican Senator Ted Cruz said in a letter seen by Reuters

the Federal Communications Commission should only approve the

deal "with specific, enforceable deployment requirements. The

United States cannot afford to let valuable spectrum remain

underutilized as demand continues to increase."

T-Mobile, Grain Management and the FCC did not immediately

respond to requests for comment.

Cruz said it was crucial that the spectrum be put to use to

address surging U.S. wireless needs, and he noted Grain's

request for a 12-year extension of its build-out obligations.

"This raises serious questions as to whether Grain intends

to quickly and efficiently put this spectrum to the highest and

best use or whether it intends to let it sit idle, wait for the

valuation to rise, and flip it for a profit," Cruz said.

"Allowing it to be held for speculation rather than deployed

undermines both our economic and national security interests."

Cruz noted that the 800 MHz spectrum T-Mobile plans to sell

"is poised for immediate, large-scale deployment." The U.S. in

2024 used a record 132 trillion megabytes of mobile data, up 35%

from the prior high of 100 trillion megabytes set in 2023,

according to CTIA, a wireless trade association.

The FCC lost authority to auction wireless spectrum for two

years in a standoff over the Pentagon's wireless spectrum.

Legislation passed last year requires the FCC to auction

spectrum in the Upper C-Band by July 2027.