President Trump invoked executive privilege over 2020 census documents related to his administration's decision to add a citizenship question to the 2020 census -- just as the House Oversight Committee was moving forward with its plan to vote on holding Attorney General William Barr and Commerce Secretary Wilbur Ross in contempt for not producing the material.

The committee's chairman, Rep. Elijah Cummings, announced Tuesday during the committee's meeting that he would delay the contempt vote until Tuesday afternoon, in order to allow members of the committee to review the Justice Department's explanation of the president's claim of privilege over the documents.

Committee Democrats say their efforts to obtain documents related to the addition of a citizenship question to the 2020 census have been thwarted by the administration for months. Although the government says that it has provided some 17,000 pages of documents to the Oversight Committee, Cummings complained that most of the documents were already public or heavily redacted.

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The Justice Department said in a letter to Cummings that by going ahead with the contempt vote, the committee has "abandoned the accommodation process with respect to your requests and subpoenas for documents" regarding the inclusion of the citizenship question.

In the letter, Assistant Attorney General Stephen Boyd advised Cummings that "the President has asserted executive privilege" over the subpoenaed documents," which Boyd said is "protective" and will "ensure the president's ability to make a final decision whether to assert privilege" after a full review of the material.

He also said that the department had explained to the committee "on several occasions" that some of the subpoenaed documents are subject to attorney-client privilege, and Boyd asserted that the department had made "ongoing and continued efforts toward accommodation," including offering Principal Deputy Assistant Attorney General John Gore for an additional interview with the committee.

Critics of the citizenship question argue that adding such a question could deter non-citizens from self-reporting, which in turn could lead to an undercount of primarily Hispanic voters in Democratic states. This could affect congressional apportionment and benefit rural, more Republican states.

This suspicion has been bolstered by the revelation that a Republican expert on gerrymandering had advocated for adding the question in order to benefit "Republicans and Non-Hispanic Whites." A report released last week found that the census could undercount more than 4 million people, particularly in Latino and African American communities.

The addition of the question is also being challenged in the Supreme Court. The Court is expected to rule on the legality of the addition this month.

Paula Reid and Grace Segers contributed to this report.