Cablevision and Verizon FiOS customers abruptly lost their access to Tennis Channel on Sunday midway through the United States Open.

The dispute revolves around a new contract between Tennis Channel and the National Cable Television Cooperative, a consortium of cable operators that Cablevision and Verizon belong to. The deal, which went into effect after midnight, requires its members to place Tennis Channel on a broad digital basic level — or not at all.

The previous contract let operators carry Tennis Channel on a level of service like a digital sports tier, which costs customers an extra monthly fee.

While Cablevision carried Tennis Channel on a sports tier, Verizon FiOs placed it on its most expensive package, called Ultimate. Tennis Channel wants its carriage to be broader.

Tennis fans’ loss of access to the channel came six days into the tournament and early on a day when the channel was showing matches from 7 to 11 p.m. Eastern. Tennis Channel and ESPN2 share the cable rights to the tournament. CBS is the over-the-air broadcaster.

The dispute between Tennis Channel and Cablevision broke into the open two years ago after negotiations broke down. Cablevision then joined the cable cooperative, which allowed it to show the channel as it wanted: on a sports tier.

In a statement on Sunday, Tennis Channel said that Cablevision became a member of the cooperative in 2009 “seemingly only to get access to Tennis Channel under terms that the network had agreed to with smaller operators seven years earlier.”

A Cablevision spokesman said in a statement that “the Tennis Channel appears to have pulled its signal off dozens of cable systems across the country, including Cablevision, after demanding significantly higher fees.”

Eric Abner, a Tennis Channel spokesman, said that the “wide majority” of the cable cooperative’s members who carried the network under the consortium’s old agreement “have chosen to continue to carry it under the new agreement.”

Verizon and Tennis Channel’s differences have been kept much quieter.

“They chose not to be part of the new N.C.T.C. deal, so they opted out and are not entitled to the signal anymore,” Abner said.

Kevin Laverty, a Verizon spokesman said, “conversations are ongoing,” but he would not predict whether the dispute will be resolved before the tournament’s end.

Abner said that negotiations are not continuing with Cablevision.