Verizon Wireless, a venture of Verizon Communications and Vodafone Group Plc, said April 18 that it would sell spectrum depending on the outcome of the FCC's pending review of its plan to pay about $3.9 billion for spectrum owned by cable operators.

The FCC said on Tuesday it needed more information on the link between both deals by May 22. It also asked Verizon Wireless for details of any efforts it made to use the spectrum it wants to sell.

The licenses Verizon Wireless bought in a 2008 FCC auction came with buildout requirements, and the FCC noted that Verizon Wireless had yet to deploy service using the spectrum.

Verizon executive Tom Tauke said last month that the looming June 2013 deadline to build out a portion of its licenses prompted the decision to sell the A and B spectrum licenses in the 700 Megahertz (MHz) frequency band.

He added that the airwaves from the cable operators were more compatible with Verizon's current spectrum holdings than the A and B block spectrum. Selling them now, he said, would give potential buyers more time to meet the buildout requirements and was not related to the proposed multibillion-dollar airwave deals with cable operators.

The company declined to comment on Tuesday's FCC inquiry.

Verizon Wireless, the largest U.S. carrier, announced plans in December to pay Comcast Corp and Time Warner Cable Inc $3.6 billion in a spectrum and marketing deal.

A similar deal with privately held cable operator Cox Communications, worth $315 million was reached later that month.

Verizon rivals Sprint Nextel, MetroPCS Communications and Deutsche Telekom AG's T-Mobile USA, all complained to the FCC about the bigger company's cable deal on concerns that it would give too much market power to the already dominant company.

Others have said the deals would create allies out of former rivals, to the detriment of consumers.

Marketing agreements accompanying the spectrum sale would create a joint entity and allow the cable operators to resell Verizon's mobile service as part of the deals.

(Reporting by Sinead Carew and Jasmin Melvin in Washington; editing by M.D. Golan)

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