(Bloomberg) -- President Donald Trump is keeping up pressure on social media giants even in the waning days of his administration.Trump on Tuesday night threatened to veto a defense bill if it doesn’t take aim at a liability shield enjoyed by the social media platforms, while on Wednesday the Senate advanced his nominee who favors weakening that shield to the Federal Communications Commission. Trump pledged to veto the annual U.S. defense bill unless Congress includes a provision to abolish the law that protects technology companies such as Twitter Inc. and Facebook Inc. from liability over most content published by their users. Trump has accused the companies of discriminating against his views. Lawmakers from both parties have pushed back on the notion and could move to override a veto.His threat drew a derisive tweet from Representative Adam Smith, of Washington, the Democratic chairman of the House Armed Services Committee.“You’re mad at Twitter. We all know it,” Smith tweeted on Wednesday. “You’re willing to veto the defense bill over something that has everything to do with your ego, and nothing to do with defense.”Each house of Congress has passed a version of the bill without language on Section 230 of the Communications Decency Act, which Trump is seeking to eliminate. The committee’s top Republican said the bill shouldn’t include extraneous issues.“The purpose of the bill has always been to support our troops and to protect American national security. Disagreements on all other issues have been put aside. This year should be no different,” Representative Mac Thornberry, of Texas, said in a statement.Lawmakers from each chamber are expected to meet in the coming days to agree on final language of the bill.Meanwhile, the Senate Commerce Committee’s Republicans advanced the FCC nomination of Nathan Simington, an administration official who helped write Trump’s proposed rule to increase social media’s exposure to lawsuits. The committee voted 14-12 along party-lines.The rule, pending at the FCC, would weaken defenses against litigation over removing or labeling user posts. Trump proposed the measure after Twitter began selective fact checks of his posts. The president and his allies have said with scant evidence that popular platforms discriminate against conservative voices.In the Senate Commerce Committee, Connecticut Democrat Richard Blumenthal said he would seek to block Simington’s nomination from a vote on the Senate floor.“It would seem that Mr. Simington is nominated for just one purpose: to support the president’s indefensible assault on the First Amendment,” Blumenthal said.If Simington’s confirmed, he would be in the FCC majority through Inauguration Day Jan. 20, then part of a 2-to-2 deadlock that could last months until the Senate confirms a Biden addition to the agency.FCC Chairman Ajit Pai, a Trump appointee, has said he will advance the Section 230 rulemaking that Simington helped to write. Pai hasn’t laid out his plans in detail and time is tight to do so.Pai would need to follow “extraordinary” procedures to adopt the matter by the time he leaves on Jan. 20, and whatever emerges would be vulnerable to reversal as Democrats take over the agency, said Andrew Jay Schwartzman of the Benton Institute for Broadband & Society.If FCC Democrats have a majority, they could simply rescind the last-minute action. Even if the agency is in a partisan tie, the FCC could refuse to defend Pai’s action against a likely legal challenge. Once the partisan tie is broken when a Biden nominee arrives, the agency could take up requests to reconsider and revoke the action, Schwartzman said in an interview.Brian Hart, an FCC spokesman, didn’t respond to telephone and email queries about Pai’s intentions.For more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2020 Bloomberg L.P.