LAS VEGAS — The pitch to television broadcasters this week was not easy for them to swallow. It is a good time, they were told, to sell their most precious resource.

With Americans increasingly turning less to over-the-air television broadcasts and more to their mobile devices, the federal government wants to devote a bigger portion of the airwaves that carry communications signals to mobile phone data.

As it turns out, some of the most desirable airwaves — those able to travel far distances and through buildings and trees — are in the hands of America’s local television stations. The government is seeking to pay stations billions of dollars to move off those airwaves, and then it plans to sell those airwaves to wireless carriers.

But if enough stations do not offer up their airwaves, also known as spectrum, the ambitious plan of the Federal Communications Commission will not take shape. And so this week, at a major conference here for broadcasters, officials from the F.C.C. went into sales mode. Consider how much money you could make, they told the stations, and consider how little you risk by sitting at the bargaining table with us.