In a national conference call, Joe Browne said the network's position will be "one of the factors" the owners will consider when they vote on the move at their annual March meeting in Phoenix next week.
Browne said the network didn't give the league specific reasons for opposing the move, but he speculated that "you could read between the lines" that the network was concerned about losing the nation's second largest television market, should the Rams start selling out again and thus avoid TV blackouts.
"They hope to have the Rams for many, many years," Browne said.
During the playoffs, Fox chairman Rupert Murdoch said he wouldn't oppose the move and added, "One of our frustrations was the blackouts in Los Angeles, because the Rams didn't fill the stadium."
There had been speculation the network might not mind the Rams leaving because it could then show national doubleheaders in the market. With two teams in the Los Angeles area, one is almost always at home, in which case NFL rules don't allow TV doubleheaders.
But Browne said that in the "long-term view," the network might be better off if the Rams stayed in Los Angeles and started winning.
If the owners vote down the move (23 votes are needed to approve the move), they will be risking an antitrust suit from the Rams.
The Raiders won a lawsuit to move from Oakland to Los Angeles in 1982, but the league later instituted guidelines that have never been tested in court.
Joe Alioto, the San Francisco attorney who won the Raiders case and is representing two former New England Patriots owners, Billy Sullivan and Victor Kiam, in antitrust suits against the league, predicted the Rams could win $300 million to $400 million in damages in a lawsuit against the league.