The Federal Communications Commission has asked US number one operator Verizon Wireless for clarification on its spectrum plans, following its previously announced deals to buy AWS spectrum from a consortium of cable companies and sell some of the 700MHz frequencies it already owns.

In a letter published by the regulator yesterday, it asks Verizon the steps it has taken to date to deploy services using the 700MHz licences in question, which include a network buildout obligation for June 2013. It also asked the operator to “explain the relevance, if any,” of the 700MHz sale plans on its investigation of the AWS transaction, including any details of previous sale efforts, and its plans if the AWS deal does not go through.

Some reports suggested that the request indicates that the watchdog has concerns about the deals, and Verizon’s approach to its spectrum holdings. At the CTIA Wireless 2012 event last week, Dan Mead, CEO of the operator, said that its moves “show that we are responsible stewards of these high value, and extremely costly assets.”

Rivals of Verizon, such as T-Mobile USA, have argued that the AWS deal is unnecessary, due to the existing spectrum holdings.

The FCC has requested a response from Verizon by 22 May 2012.