The Patriots-Giants game, which was to be broadcast Saturday night to less than half the country by the NFL Network, will be available to the entire nation under an agreement reached Wednesday by NBC and CBS to simulcast it.

The 15-0 Patriots are attempting to become the first National Football League team since the 1972 Miami Dolphins to go undefeated throughout the entire regular season. Miami went on to win the Super Bowl and finish 17-0 that season.

NBC and CBS will show the NFL Network’s production of the game, with the announcers Bryant Gumbel and Cris Collinsworth, and will not pay an extra rights fee. They will each get to sell 18 30-second commercial units.

Dick Ebersol, the chairman of NBC Universal Sports, said yesterday by telephone that in a conversation in October with Steve Bornstein, the chief executive of the NFL Network, that he would be amenable to a simulcast, and would share it with another broadcast network, if the Patriots’ momentum toward an undefeated season continued. Then, on Monday morning, Bornstein called to ask him if his idea was still viable for NBC.