By Ronald Grover and Liana B. Baker

LOS ANGELES/NEW YORK (Reuters) - The National Football League is asking television networks that currently televise its games to bid on a package of Thursday night matchups, a process that in the past has produced bidding wars for the hugely popular U.S. sport.

Brian Rolapp, NFL Media's chief operating officer, confirmed that requests for proposal were sent to broadcast and cable companies, including the NFL's current partners.

The NFL is seeking bids for as many as eight of the games currently telecast on the league-owned NFL Network in an effort to get higher ratings than those on its cable channel, according to two people with knowledge of the requests.

Formal requests for proposal went out to Disney's ESPN cable network, which shows games on Monday night, and to Comcast's NBC network, CBS and to Twenty-First Century Fox's Fox network, all of which show regular season games, mostly on Sundays.

The league also sent out requests to other TV outlets, according to one person with knowledge of the bids. Recipients of those bids couldn't be determined, but one is believed to be Time Warner's Turner Broadcasting System, whose channels televise pro basketball and baseball games.

Google, which had expressed interest in streaming NFL games in the past, was not asked to bid, according to the person.

The league wants to boost ratings for the Thursday night games to give them the same prominence the league enjoys for its games on Sunday and Monday nights, according to a person with knowledge of the NFL's thinking.

NFL Network's Thursday night games were viewed by an average of 8 million viewers for a 13-game schedule in 2013, a 10 percent boost from 2012 but still far below NBC's average 21.5 million viewers for its Sunday night contests.

WIDER AUDIENCE

The league's network is available in more than 72 million homes, fewer than ESPN and less than the reach of the broadcast networks.

The NFL is seeking bids for a single season, starting this September, people familiar with the matter said, with the likelihood of extending the contract after its first year. NFL Network would televise games not included in the new contract.

Based on the reported $950 million that NBC pays for its package of 19 NFL Sunday night games, an eight-game lineup could be worth $400 million or more.

The league will determine how many Thursday night games it will offer based on the specific proposals it receives, and may also include late-season Saturday contests, said one person with knowledge of the league's thinking.

The NFL hopes its existing partners will aggressively promote the games on their other media properties, and improve their production quality, according to one person with knowledge of the bidding process.

As fewer people watch live TV, NFL games have become among the most valuable media properties for networks and reap hundreds of millions of advertising dollars.

Representatives for ESPN, CBS, NBC, Fox and Turner declined comment.

(Reporting by Ronald Grover in Los Angeles and Liana B. Baker in New York; Editing by Eric Walsh)