President Trump said on Thursday that he had ordered the Commerce Department to begin work on a new census that excludes undocumented immigrants.

A new census would be a significant departure for a process stipulated by the Constitution to occur every 10 years. Historically, the census has counted all U.S. residents regardless of their immigration status, a process that helps determine both the allotment of congressional seats and billions of dollars in federal money sent to states.

“People who are in our Country illegally WILL NOT BE COUNTED IN THE CENSUS,” Mr. Trump wrote in a post on social media.

The push comes as Mr. Trump and his allies press Republican-led states to redraw their congressional maps to benefit the party. Congressional maps are redrawn after the census is completed based on the new data. The next census is scheduled for 2030.

Mr. Trump tried a similar move in 2020 to keep undocumented immigrants out of the census, but a federal court rejected that attempt, and the Supreme Court declined to intervene, saying at the time that doing so was premature. The president’s efforts to exert pressure on the Census Bureau, which is part of the Commerce Department, were also unsuccessful.

A spokesman for the Commerce Department did not immediately respond to a request for comment on Thursday.

Later in the day, Vice President JD Vance is scheduled to travel to Indianapolis to meet with Gov. Mike Braun of Indiana and other top Republicans in the state to discuss redistricting. Mr. Trump and his allies have grown frustrated with their resistance to redraw maps to benefit Republicans.

Mr. Trump and his allies are engaged in other pressure campaigns in Texas, Missouri and Ohio as they try to squeeze out any additional seats before the midterm elections next year. With Republicans holding only a narrow majority in the House, they are worried that Democrats will regain control, start investigations into Mr. Trump and his administration, and hobble any legislative goals.