WASHINGTON — President Donald Trump is on a Twitter tirade ahead of his White House “Social Media Summit” gathering of mostly conservative groups.

Trump tweeted Thursday morning against social media companies, the press and his Democratic rivals, while calling himself “so great looking and smart, a true Stable Genius!”

Trump says a “big subject’ of Thursday’s summit “will be the tremendous dishonesty, bias, discrimination and suppression practiced by certain” companies.

Google, Facebook and Twitter weren’t invited to the event, their representatives have confirmed.

Trump has an estimated 61 million followers on Twitter. He has accused Twitter of making it “very hard for people to join me” and “very much harder for me to get out the message.” He has suggested the companies may be acting illegally and should be sued by U.S. regulators.

Trump frequently lashes out at the press, and did so again Thursday, tweeting that, “Fake News is not as important, or as powerful, as Social Media” and predicting outlets “will quickly go out of business” when he leaves office. He asserted that “even Social Media would be driven out of business” if he loses in 2020.

The White House conference offers Trump a chance to play to his conservative base in the lead-up to the 2020 election.

Among the conservative organizations that are expected to participate in the White House meeting: Turning Point USA; PragerU, short for Prager University, which puts out short videos with a conservative perspective on politics or economics; and the Washington think tank Heritage Foundation.