Tucker Carlson, who was Fox News' biggest star until his abrupt firing last month, says he's taking his show to Twitter.

He made the announcement, appropriately enough, in a tweet.

"There aren't many platforms left that allow free speech. The last big one remaining in the world — the only one — is Twitter," he said. "Twitter has long served as the place where our national conversation incubates and develops. Twitter is not a partisan site. Everybody's allowed here, and we think that's a good thing."

The announcement comes two weeks after Carlson was booted by Fox News, where he started as a contributor and, in recent years, rose to fame as the solo host in a coveted primetime slot. Fox has not yet announced a permanent replacement. Since Carlson's departure, ratings have plunged in the 8 p.m. ET slot and in the hours that follow him.

A fight with Fox News over being sidelined until 2025

Carlson and the network have yet to work out the terms under which he departs, which could complicate or thwart his plans. On Tuesday afternoon, Axios reported that Carlson's lawyer warned Fox that it cannot enforce the non-compete provision in his contract that prohibits him from hosting a show outside of Fox until early 2025. Axios reports the attorney, Bryan Freedman, says Fox has already breached the contract.

A Fox spokesperson said neither the network nor parent company Fox Corp. are commenting on the letter.

Twitter's controlling owner, Elon Musk, hinted at contractual concerns Tuesday evening, hours after Carlson's video post. "On this platform, unlike the one-way street of broadcast, people are able to interact, critique and refute whatever he or anyone may say," Musk tweeted. "I also want to be clear that we have not signed a deal of any kind."

Carlson's ouster was announced less than a week after Fox settled a defamation case filed by Dominion Voting Services for $787.5 million over lies Fox broadcast alleging fraud in the 2020 race that Trump lost. Carlson was among the hosts whose private messages figured prominently in the case. The company pushed Carlson out in a desire to tidy up messes and move on, according to three people with direct insight into decisions made there.

Carlson is also the focus of an ongoing federal lawsuit in the Southern District of New York filed by one of his former senior producers. She alleges a workplace rife with bigotry, anti-Semitism and sexism. (Carlson tells NPR he knows nothing about her. Fox says her accusations are meritless.)

The former producer, Abby Grossberg, voluntarily dropped a related case against Fox and Carlson in Delaware on Tuesday; her attorneys released a statement saying she would fold those accusations into her case in New York.

Major advertisers had already abandoned Carlson's Fox News show, which regularly embraced groundless conspiracy theories and made appeals broadly found to be racist, xenophobic and misogynistic.

Carlson had Elon Musk on his show just before Dominion settlement

Days before the Dominion settlement, Carlson hosted Musk on his Fox show in a two-night special. It included an exchange in which the two laughed about Musk's comparing the New York Times to diarrhea.

Twitter sent its now-standard reply to press requests — a poop emoji — in response to NPR's emailed request for a comment for this story. Musk did not return emails sent directly to him seeking more information about Carlson's announcement.

Some critics say such a deal is fitting for Musk, who has shown great contempt for news outlets.

"News that Tucker Carlson is moving his show to Twitter is not even surprising," said Nora Benavidez of the progressive nonprofit Free Press, an advocacy group active on media issues. "It's just the latest in a long line of dangerous actions Musk takes to erode open discourse and public trust surrounding the platform."

"Twitter is becoming a fringe network which places hyper-partisanship, lies, and hate over application of corporate policies and robust trust and safety," Benavidez added.

Since his ouster from Fox, Carlson had been wooed openly by numerous conservative and right-wing outlets, including Glenn Beck's The Blaze, Newsmax and others.

In announcing his deal with Twitter, Carlson had a sharp rebuke for all news outlets, which he referred to as "gatekeepers."

"The best you can hope for in the news business at this point is the freedom to tell the fullest truth that you can," Carlson said in his video post explaining why he's seeking to head to Twitter. "But there are always limits, and you know that if you bump up against those limits often enough, you will be fired for it. That's not a guess. It's guaranteed."

Twitter, he said, was among the last places to find true freedom of expression.