Fox Networks Group is preparing to warn customers of a possible blackout of its channels on Charter Communications systems this weekend as talks between the two companies on a new carriage agreement have stalled.

Sources tell Variety that Fox will begin running an ad campaign Thursday evening informing Charter’s Spectrum customers that they may lose access to Fox cable channels — including FX, National Geographic, and Fox Sports — as soon as this weekend.

“Fox and Charter Spectrum have an agreement to carry the Fox networks that Charter has chosen to ignore,” a Fox spokesperson said in a statement. “We are disappointed that despite our best efforts over many months to resolve the situation without disruption, Charter’s 16 million subscribers may lose access to a wide variety of programming, including telecasts of the St. Louis Cardinals and Blues, Kansas City Royals, Cleveland Cavaliers, Cincinnati Reds and many other MLB, NBA and NHL teams on Fox Regional Sports Networks, FX’s hit dramas ‘The Americans’ and ‘Feud,’ and National Geographic.”

The dispute rises from Charter’s acquisition last year of Time Warner Cable. Beginning in May, when the acquisition was finalized, Charter began paying affiliate fees according to Time Warner Cable carriage contracts, which generally assigned a more favorable rate for the distributor. That move is the subject of lawsuits involving networks including Univision, Showtime, and Fox News, whose parent companies claim that the Charter contracts should remain in effect. Fox Networks’ deal with Time Warner expired March 31. The two companies have been in sporadic negotiations on a compromise deal for the last eight months.

But with no deal in place besides the legacy Charter agreement, Fox claims that Charter is in breach. The company is threatening to pull its channels Friday night.

“Fox is trying to gouge our customers using the increasingly common tactic of threats and removal of programming,” a Charter spokesperson said in a statement. “They are attempting to extort Charter for hundreds of millions of dollars. We will continue to work towards a fair agreement.​”

If a blackout were to happen, Fox would be the one to initiate it with a decision to cut its feed to Charter.

Public-pressure campaigns are frequent components of cable negotiations. In December, NBCUniversal launched a similar campaign in its own carriage standoff with Charter. The two parties came to a renewal agreement a little more than two weeks later, averting a blackout.