U.S. President Donald Trump speaks to members of the media before boarding Marine One on the South Lawn of the White House in Washington, D.C., U.S., on Tuesday, June 11, 2019.

President Donald Trump on Wednesday asserted executive privilege over information related to his administration's decision to add a citizenship question to the 2020 census as the House Oversight Committee prepared to hold two of his Cabinet members in contempt for defying its subpoenas on the issue.

Trump's move, which the Justice Department announced in a letter to the committee's chairman, Elijah Cummings, came as the panel began a meeting to vote on a resolution to hold Attorney General William Barr and Commerce Secretary Wilbur Ross in contempt of Congress for withholding documents on the decision to add the question to the census.

The resolution would allow Democrats to pursue both civil and criminal contempt of both Cabinet officials for defying subpoenas issued by Cummings, D-Md., on April 2 to produce the documents. Democratic leadership and House counsel would then decide which avenue to pursue.

"What we have learned in this investigation is quite disturbing," Cummings said in his opening remarks, stating that the committee obtained evidence that Ross was "aggressively pressing his staff" to add the citizenship question to the 2020 census months before the DOJ made the request to include it, and that Ross did so at the urging of the White House.

Cummings said the administration has claimed that it has supplied 17,000 pages of documents on the issue to the committee.

"This is true, but the vast majority of these documents were already public; others were heavily redacted," he said.

Rep. Jody Hice, R-Ga., a member on the committee, said lawmakers should not vote on a contempt resolution until the public gets a clear understanding of why Democratic lawmakers oppose adding the question.

"The American people need to know what's going on here," Hice said. "Democrats simply don't want to have a citizenship question, and it is important for us to ask why. We know that that question cannot be used for immigration enforcement. It cannot be used for deportation. These types of things are in federal law. So the question is, why do the Democrats not want to know how many citizens are in this country?

Those who oppose adding the question say it would likely suppress the response rate in immigrant communities, leading to an undercount. The administration, meanwhile, has argued that including the question would help it to enforce the Voting Rights Act.

To take action in criminal contempt, the House would need to hold a full floor vote. For civil contempt, Democrats would seek authorization from a bipartisan group of House leaders, in which Democrats hold the majority, to file a lawsuit to enforce the committee's subpoenas.

The committee, which had planned to vote on the resolution Wednesday morning, postponed action until the afternoon to allow members to read the Justice Department letter stating why the president had asserted executive privilege.

On Tuesday, the Justice Department had warned Cummings in a letter that it would recommend the president assert executive privilege if the House voted to hold the officials in contempt of Congress.

Rep. Jim Jordan, R-Ohio, the top Republican on the Committee, also sent a letter to Cummings Tuesday charging that the chairman had rushed to hold a contempt of Congress vote, and had violated committee rules in scheduling the vote. He argued that "both Attorney General Barr and Secretary Ross have cooperated — and continue to cooperate — with your investigation."

The planned committee vote comes a day after the House approved a resolution to authorize the House Judiciary Committee and other panels to go to court to enforce their subpoenas of the Trump administration.

That measure, which was adopted 229-191 along party lines, allows the Judiciary Committee to sue Barr and former White House counsel Don McGahn for refusing to comply with its subpoenas related to former special counsel Robert Mueller's report on Russia's efforts to influence the 2016 election and possible obstruction of justice by Trump.

The Judiciary Committee voted in May to advance a measure to hold Barr in criminal contempt of Congress, but Chairman Jerry Nadler, D-N.Y., said Monday that he would hold off on that threat after reaching an agreement with the Justice Department to obtain some underlying evidence from the Mueller report related to possible obstruction of justice by Trump.

Cummings said the House vote Tuesday "marks a pivotal moment for Congress in our ability to conduct oversight as an independent branch of government."

The White House, Cummings said, has "not turned over one single shred of paper in response to any of our requests" about such things as the response to Hurricane Maria in Puerto Rico; executive branch security clearance concerns; efforts to transfer nuclear technology to Saudi Arabia; and hush money payments that the president's former longtime lawyer, Michael Cohen, made to women who allege past affairs with Trump, which he has denied.