WASHINGTON (AP) — Fox News sent Tucker Carlson a cease-and-desist letter over his new Twitter series, Axios reported Monday, amid reports of a contract battle between the conservative network and its former prime-time host.

Carlson was ousted from Fox in late April, less than a week after Fox agreed to pay Dominion Voting Systems nearly $800 million to settle an explosive defamation case. The network provided no explanation for the firing, but a wave of reports on damaging text messages and other statements Carlson made during his time at Fox have since piled up.

Since leaving Fox, Carlson kicked off a "Tucker on Twitter" series — arguing that Twitter was "the only" major remaining platform that allows free speech as he denounced news media. The series, which has published two episodes so far, has appeared to escalate contract tensions between Carlson and Fox.

Fox has demanded Carlson stop posting videos to Twitter, The New York Times also reported Monday — as the network's lawyers accuse Carlson of violating his contract, which runs until early 2025 and restricts his ability to appear on other media outlets. Meanwhile, Carlson's lawyers have said the network breached the contract first.

A spokesperson for Fox News Media and attorneys representing Carlson, Bryan Freedman and Harmeet Dhillon, did not immediately return The Associated Press' requests for comments on Tuesday.

"Doubling down on the most catastrophic programming decision in the history of the cable news industry, Fox is now demanding that Tucker Carlson be silent until after the 2024 election," Dhillon said in a statement sent to Axios and the Times. "Tucker will not be silenced by anyone."

Before his April firing, Carlson was Fox's top-rated host. His stew of grievances and political theories grew to define the network over recent years and made him an influential, and widely controversial, force in GOP politics.

Carlson has previously come under fire for defending a white-supremacist theory that claims white people are being "replaced" by people of color, as well as spreading misinformation about issues ranging from the Jan. 6 attack on the Capitol to Russia's war in Ukraine.