A Silicon Valley company has asked the U.S. government to give it a band of radio spectrum for a free high-speed wireless Internet network that would cover most of the United States and be supported by advertising.

The idea is to create something like an Internet version of broadcast television, using local and national sponsors to pay for what its promoters say would be nearly ubiquitous high-speed access.

The company, M2Z Networks, is backed by several prominent Silicon Valley venture capitalists. It is making a case that its plan could hasten the spread of broadband Internet use and lead to lower prices by spurring competition with the cable and telephone giants that dominate the Internet market.

But the idea’s success depends entirely on something that its backers cannot control and that some telecommunications analysts say they are unlikely to get: cooperation from the Federal Communications Commission.

In its filing with the agency, M2Z said that the spectrum it sought was not scheduled for auction and could wind up going to waste because it might not be easily used for other functions, like transmitting cellphone calls.

But the spectrum would be enough to deliver the company’s proposed free Internet access at 384 kilobits a second, about six times the speed of dial-up, said Bruce Sachs, a partner with the venture capital firm Charles River Ventures. Sachs said his firm was one of three that backed M2Z in January with a round of financing. He did not disclose the amount raised.

Backers have apparently committed $400 million to the project — if approval is forthcoming from the FCC. Projected total cost for the 10-year project is $1 billion.