Senator Ted Cruz urged the Federal Communications Commission to impose enforceable deployment requirements on T-Mobile's planned sale of wireless spectrum assets to Grain Management, Reuters reported Monday.

T-Mobile agreed last year to sell its portfolio of 800 MHz licenses to Grain Management for $2.9 billion in cash and Grain's 600 MHz spectrum licenses. Cruz said the FCC should approve the transaction only with conditions ensuring the spectrum is put to use.

In a letter seen by Reuters, Cruz cited Grain's request for a 12-year extension of its build-out obligations and questioned whether the firm intends to deploy the spectrum promptly.

"Allowing it to be held for speculation rather than deployed undermines both our economic and national security interests," Cruz wrote, according to Reuters.