President Donald Trump on Tuesday threatened to veto a nearly trillion dollar annual defense bill unless Congress repeals the federal law that spares Facebook, Google and other social-media sites from legal liability over their content-moderation decisions.

Trump delivered the ultimatum targeting the digital protections, known as Section 230, in a late-night tweet that marked a dramatic escalation in his attacks against Silicon Valley over unproven allegations that the country’s tech giants exhibit bias against conservatives.

“Section 230, which is a liability shielding gift from the U.S. to ‘Big Tech’ (the only companies in America that have it – corporate welfare!), is a serious threat to our National Security & Election Integrity,” Trump tweeted.

Unless the “very dangerous & unfair Section 230 is not completely terminated as part of the National Defense Authorization Act (NDAA),” Trump continued, “I will be forced to unequivocally VETO the Bill when sent to the very beautiful Resolute desk.”

Section 230 is a decades-old federal law that spares websites from being held liable for their decisions about the posts, photos, videos and other content they take down or leave online. It is considered one of the web’s foundational laws, crafted in large part to facilitate free expression.

Many lawmakers – Democrats and Republicans – have sought to repeal Section 230 in recent years to hold tech giants accountable for failing to police a wide array of harmful content, including hate speech and election disinformation. But Trump and his Republican allies have seized on the debate to advance their arguments that Facebook, Google, Twitter and others exhibit political bias against conservatives – a charge for which they have provided little evidence, and one that the companies themselves deny.

Trump has ratcheted up his attacks as social-media companies have taken more aggressive action against his most controversial posts, including his tweets falsely claiming he won the 2020 presidential election. Tying the fight to the NDAA, a must-pass defense bill, threatens to inject a heavy dose of partisan politics into an annual national security debate.