Verizon Wireless, the largest US mobile provider, should be prevented by federal regulators from buying airwaves from cable companies to avoid “excessive concentration” of spectrum, T-Mobile USA said.

Two airwaves purchases totaling more than $3 billion proposed by Verizon “pose a clear threat to competition,” T-Mobile, the fourth-biggest US wireless carrier, said in a filing to the Federal Communications Commission.

The purchases would keep smaller competitors from using the airwaves for advanced services, according to T-Mobile, which AT&T unsuccessfully tried to buy last year.

Verizon proposed in December acquiring airwaves for $3.6 billion from top US cable operator Comcast Corp., No. 2 Time Warner and Bright House Networks LLC, and announced a separate $315 million spectrum purchase from Cox Communications. Under the transactions, Verizon and the cable companies would market and sell each other’s services.

Ed McFadden, a Verizon spokesman, said in an e-mailed statement yesterday that “the spectrum purchase is in the public interest, and will address the needs of all consumers, putting spectrum to work to meet growing demand.”

Sprint Nextel Corp., the third-largest US mobile-phone provider, and leading satellite TV company DirecTV asked the FCC to examine the marketing arrangements.