NBC reached a nine-year extension with the National Football League to broadcast Sunday night games, securing rights to its top-rated prime-time show through 2022.

NFL agreements also were signed with CBS and Fox. Industry sources say the deals could cost, on average and over the life of the agreements, about $1 billion a year for each network, or 50 percent more than the estimated current NFL tab.

The NFL said the deals would keep the hugely popular games on free, over-the-air television. NBC says that Sunday Night Football - introduced by country-music star Faith Hill - is the top-rated prime-time show on any broadcast TV channel this year.

"There is no more powerful programming on television than the NFL and no better program than Sunday Night Football," said Steve Burke, CEO of NBCUniversal.

Comcast Corp. controls NBC through NBCUniversal, which it owns with General Electric.

The deal is Comcast's second blockbuster sports deal. In June, the company purchased U.S. television rights for the Olympics through 2020 for $4.4 billion.

NBC expanded its NFL package in the new deal, adding a Thanksgiving night football game previously broadcast on the NFL Network, and upgraded its playoff rights.

The new Thanksgiving night game will begin showing on NBC in 2012. Instead of NBC showing two wild-card playoff games, the network will show two division playoff games.

NBC also will show three Super Bowl games - in 2015, 2018, and 2021 - with the new contract, along with airing the 2012 Super Bowl under the existing contract.