Census worker Marisela Gonzales adjusts a sign at a U.S. Census walk-up counting sight set up for Hunt County in Greenville,…
FILE - Census worker Marisela Gonzales adjusts a sign at a U.S. Census walk-up counting site set up for Hunt County in Greenville, Texas, July 31, 2020.

The Census Bureau plans to announce it will miss a year-end deadline for handing in numbers used for divvying up congressional seats. That delay could undermine President Donald Trump's efforts to exclude people in the country illegally from the count if the figures aren't turned in before President-elect Joe Biden takes office.

It will be the first time that the December 31 target date has been missed since Congress implemented the deadline more than four decades ago.

Internal documents obtained this month by a House committee show that Census Bureau officials don't see the apportionment numbers being ready until days after Biden is inaugurated on January 20.

Once in office, Biden could rescind Trump's presidential memorandum directing the Census Bureau to exclude people in the country illegally from numbers used for divvying up congressional seats among the states. An influential GOP adviser had advocated excluding them from the apportionment.