Google has asked the US Federal Communications Commission (FCC) to block the sale of the 700MHz spectrum to Verizon unless the company pledges to make a section of the spectrum available to all.

Google said originally that it would purchase the spectrum to make sure that it was not used in such a way as to stifle competition.

In particular the search giant was trying to get the purchaser to make sure that customers would not be locked into using a limited number of devices to access the spectrum.

Verizon opposed such a move before the auction, but the FCC made it a condition of the sale that at least part of the spectrum would remain open. Verizon started legal action to get this condition dropped but has since backed down.

"It is necessary and appropriate to ensure that Verizon and all interested parties clearly understand the FCC's C Block condition at this time," said Google in a filing with the FCC.

"Further, for the sake of its own public interest findings, and to ensure that investment and innovation is properly directed to the C Block, the FCC must ensure in this proceeding that Verizon stands ready to meet its obligations upon grant of its C Block licences."

Google has urged the FCC to obtain concrete plans from Verizon before allowing the sale, and has asked that the sale be blocked if such commitments are not given.