An extension to a simulcasting contract between Las Vegas casinos and most of the tracks owned by Churchill Downs Inc. and Magna Entertainment Corp. expired as of midnight on Sunday, introducing the possibility that a blackout of the signals in the racebooks would begin on Wednesday. TrackNet, a simulcast-marketing partnership co-owned by Magna and Churchill, is pressing the casinos to pay a higher rate for its signals, and the casinos have balked. Two tracks owned by Magna Entertainment - Gulfstream Park and Santa Anita Park - are dark on Monday and Tuesday and will not be affected by the expiration until Wednesday. Fair Grounds, owned by Churchill Downs, is covered under a contract separate from the expired agreement, according to Kevin Flanery, the vice president of communications for Churchill. The signal from Fair Grounds was available in the casinos on Monday and will be throughout its meet, Flanery said. TrackNet, a simulcast-marketing partnership co-owned by Magna and Churchill, granted the extension early in January so that the casinos would have the Santa Anita and Gulfstream signals through the National Handicapping Championship, held in Las Vegas this past weekend. Since then, TrackNet has been unable to reach a deal with the Nevada Pari-Mutuel Association, which represents approximately 80 race books in the state. Officials for TrackNet and the parimutuel association did not return phone calls on Monday. TrackNet is pressing the casinos to pay a higher rate for its signals, and the casinos have balked. A handful of other financial issues related to who pays the costs of simulcasting are also in the negotiating mix, according to officials.