William Barr, U.S. attorney general, speaks during a Senate Judiciary Committee hearing in Washington, D.C., U.S., on Wednesday, May 1, 2019.

The U.S. Justice Department suggested on Tuesday that it may completely withhold special counsel Robert Mueller's unredacted report from Congress if the House moves ahead with plans to hold Attorney General William Barr in contempt.

The department said in a letter to House Judiciary Committee Chairman Jerrold Nadler that any move by Democrats to hold Barr in contempt would compel the attorney general to "request that the President invoke executive privilege" over the unredacted materials in Mueller's report that the Democrats previously subpoenaed.

In addition to that, the DOJ letter asks the Committee to cancel the contempt markup and suspend enforcement of the subpoena.

"In the face of the Committee's threatened contempt vote, the Attorney General will be compelled to request that the President invoke executive privilege with respect to the materials subject to the subpoena. I hereby request that the Committee hold the subpoena in abeyance and delay any vote on whether to recommend a citation of contempt for noncompliance with the subpoena, pending the President's determination of this question," said the letter, signed by Assistant Attorney General Stephen Boyd, which was obtained by NBC News from a source on the committee.

In response, Nadler said in a statement that "this kind of obstruction is dangerous," and insisted that "the Committee will proceed with consideration of the contempt citation as planned."

"The Department's decision reflects President Trump's blanket defiance of Congress's constitutionally mandated duties," Nadler said. "In the coming days, I expect that Congress will have no choice but to confront the behavior of this lawless Administration. The Committee will also take a hard look at the officials who are enabling this cover up."

— NBC News and Reuters contributed to this report