Trump’s threat, which represented an escalation of his previous rhetoric targeting the tech giants for purported bias against conservative expression, came after Twitter flagged two of his posts on Tuesday with fact-check warnings. Those messages falsely asserted absentee ballots are likely to be “substantially fraudulent.”

The president later in the day lashed out against the company for the first-of-its-kind intervention on his social media feed, declaring online that Twitter “is now interfering in the 2020 Presidential Election” and “completely stifling FREE SPEECH.”

Facebook, Twitter and other high-profile titans of the tech industry have come under bipartisan criticism by congressional lawmakers in recent years for their use of Americans’ personal data. Additionally, Democrats accuse the social media platforms of insufficiently countering the spread of misinformation, while Republicans charge that the companies disproportionately seek to silence conservative opinions.

Last year, the Trump administration asked social media users to report directly to the White House if they believed companies like Facebook and Twitter had punished them for their political views. However, the White House did not disclose what the administration planned to do with the material it collected, contributing to suspicions that the effort was designed mainly to harvest email addresses for the president’s reelection campaign.

Public-interest groups and civil liberties advocates say there is no clear evidence that tech companies suppress conservative viewpoints.