Competitors of Verizon Wireless are asking US communications regulators to block the company’s proposed deal to buy wireless airwave rights held by cable companies for $3.9 bn.

Companies including Sprint Nextel Corporation, T-Mobile USA and MetroPCS Communications voiced their concerns, saying the the deal would result in "an excessive concentration" of spectrum holdings, according to Reuters.

The companies said that the transaction will pose a clear threat to competition and keep smaller competitors from getting the airwaves for advanced services.

Verizon spokesman Ed McFadden was quoted as saying 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.

The US carrier Verizon Wireless proposed to acquire airwaves from Comcast Corporation and Time Warner Cable in December.

Verizon announced another $315m worth spectrum purchase deal with private cable operator Cox Communications in mid-December.

The Federal Communications Commission (FCC) will determine if the two deals meet public’s interest, while the US Justice Department will probe the antitrust grounds.

Verizon Wireless said the deal will provide it with more spectrum to serve wireless devices including smartphones that need high bandwidth.