House Republican leaders labored on Wednesday to win over holdouts for their sweeping domestic policy bill to deliver President Trump’s agenda, slogging through a marathon overnight committee session to prepare the measure for a floor vote.

The powerful Rules Committee began meeting after midnight on Wednesday morning and continued debating the measure as morning broke, while Republicans worked behind the scenes to hammer out enough concessions to cobble together the votes in their fractious ranks to push it through the House.

But as the session dragged into its eighth hour, they had yet to release any new language and the panel had yet to vote to send the legislation to the floor.

Any changes to what Mr. Trump calls the “big, beautiful bill,” would spring from extensive negotiations between Speaker Mike Johnson and Republicans from disparate factions who have so far refused to back the legislation.

“We’re meeting in the dead of night to consider a terrible bill, and you haven’t even drafted or shared some of the most critical parts of the bill,” Representative Mary Gay Scanlon, Democrat of Pennsylvania, said at 2:40 a.m.

Should the bill advance from the committee to the House floor, it could receive a vote as early as Wednesday. But as the panel’s work stretched on, it was not clear when Republicans would be able to call it up, and its prospects on the floor were far from assured.