President Trump said Sunday he won't sign any bills until Congress passes the SAVE America Act, which would require proof of citizenship and photo ID to vote.Why it matters: Trump has pushed for sweeping changes to how Americans vote ahead of midterm elections that could decide the fate of his presidential agenda.Driving the news: "It must be done immediately. It supersedes everything else," the president wrote on Truth Social.While Trump threatens to create his own gridlock, lawmakers remain at an impasse on funding the Department of Homeland Security. Even if they did reach a deal, Trump's pledge could presumably mean he wouldn't sign it.He also called for provisions to further restrict mail-in voting and gender-affirming care not already in the House-passed version.It's unclear if he's asking for new legislation to encompass those demands. The White House did not immediately respond to Axios' request for clarification, nor did it answer Axios' inquiry into whether the president would refuse to sign a DHS funding bill.Reality check: If the president does not sign a bill within 10 days of presentment while Congress is in session, it automatically becomes law.But if Congress adjourns while the bill is awaiting signature, the unsigned bill dies.Zoom in: In his post, Trump applauded conservative activist Scott Presler for encouraging the Senate to use a talking filibuster to pass the bill, which cleared the House last month.Senate Majority Leader John Thune has expressed skepticism about the tactic, which he says would require unity among the Republican conference. Republicans have framed the effort as necessary to stop noncitizen voting, but that is both illegal and rare, Axios' Jason Lalljee writes.Friction point: "[S]o be it," Senate Minority Leader Chuck Schumer (D-N.Y.) responded to the president's post."Senate Democrats will not help pass the SAVE Act under any circumstances."Rep. Maxwell Frost (D-Fla.) was more dismissive, noting on X that Congress "ain't passing any bills anyways so" — a nod to the broader legislative dysfunction that preceded Trump's threat.Go deeper: How the SAVE America Act could impact 21 million voters