For the first time in more than four decades, the US Census Bureau missed a Thursday deadline to deliver a population count of each state that is used to decide representation in the House of Representatives.

The delay could undermine US President Donald Trump's efforts to exclude people in the country illegally from the count if the figures are not submitted before President-elect Joe Biden takes office on Jan 20.

The agency plans to deliver the population count of each state in early 2021, as close to the missed deadline as possible, it said in a statement late on Wednesday.

The Associated Press reported that Census Bureau officials do not expect the apportionment numbers to be ready until days after Biden is inaugurated on Jan 20.

If the count is completed during Trump's presidency, he may attempt to exclude some undocumented immigrants for the division of House seats. The Supreme Court recently overturned rulings that would have blocked that policy.

But if the count is completed after Biden takes office, he is expected to rescind Trump's presidential memorandum directing the bureau to exclude counting those in the country illegally.

The AP said "an influential GOP adviser had advocated excluding them from the Census Bureau's count in order to favor Republicans and non-Hispanic whites". AP didn't name that adviser.