House Democrats have agreed to postpone their imminent deadline for President Trump to turn over years of financial documents pending a court ruling on his lawsuit to block such a release, handing a major victory to the White House and, for now, vindicating Trump's decision to take the matter to court.

Trump's lawyers on Monday sued to block a subpoena issued by members of Congress to the accounting firm Mazars USA LLC for an array of Trump's financial information, including annual statements, periodic financial reports and independent auditors reports.

Mazars produced, among other documents, “statements of financial condition” for Trump before he became president, outlining his net worth in ways Democrats have charged may have been intentionally misleading.

Trump's suit named Rep. Elijah Cummings, the Democratic chairman of the House Committee on Oversight and Reform, and Peter Kenny, the chief investigative counsel of the House committee, as its plaintiffs. The complaint, filed in a Washington federal court, argued that the subpoena "has no legitimate legislative purpose"and is simply intended to harass the president.

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A hearing in the case has been set for May 14, and Democrats have agreed to delay the response date on their subpoena until seven days after the court issues a ruling.

Separately, the administration defied a demand from Ways and Means Committee Chairman Richard Neal, D-Mass., to turn over six years of Trump's tax returns by the close of business on Tuesday.

Treasury Secretary Steven Mnuchin said in a letter to Neal on Tuesday that he was waiting for a Justice Department opinion on whether it is permissible to turn over the president's returns to Congress without his consent, and that a final decision is expected by May 6.

Mnuchin made clear in no uncertain terms, though, that the Democrats' request was "unprecedented," and that ordinary requests from Congress for taxpayer information were efforts to inform tax law drafting -- not to expose the private information of a particular taxpayer.

Mnuchin also argued that while Democrats claim they are acting in their oversight capacity, there has been an ongoing effort for several years, by various actors, to expose Trump's returns "for the sake of exposure" and politicial gain.

Mnuchin wrote that the Treasury Department does not share Democrats' "confidence that there is no limit to the willingness of the courts to accept obviously pretextual legislative justifications for information demands -- particularly when private tax information is at risk."

While Mnuchin noted that IRS provisions grant Congress the authority in some cases to obtain tax information, he pointed out that "the law does not allow Congress to set a deadline for the response for this request of a person’s tax returns.”

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The Trump administration generally has signaled that Democrats' efforts to obtain the tax returns will be fruitless. Acting White House Chief of Staff Mick Mulvaney had told "Fox News Sunday" earlier this month that Democrats would "never" see the returns.

Mnuchin got into a fiery viral exchange with U.S. Rep. Maxine Waters, the Financial Services Committee chair, just weeks ago at a televised hearing that touched on the issue.

Neal hasn't announced next steps after sending two letters to IRS Commissioner Charles Rettig demanding Trump's taxes. But he could opt next to issue a subpoena to enforce his demand, sent under a 1924 law that requires the Treasury secretary to furnish any tax return requested by a handful of lawmakers with responsibility over the IRS.

In another parallel congressional probe, Cummings, D-Md., has said the White House is in "open defiance" of his panel after lawyers advised a former official to ignore a separate subpoena related to the committee's investigation of White House security clearances.

Cummings said Tuesday in a statement that "it appears that the president believes that the Constitution does not apply to his White House, that he may order officials at will to violate their legal obligations, and that he may obstruct attempts by Congress to conduct oversight."

He added the White House "has refused to produce a single piece of paper or a single witness" in any of the panel's investigations this year. Democrats took control of the House in January.

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Cummings said he is consulting with other lawmakers and staff about scheduling a vote to hold former White House personnel security director Carl Kline in contempt of Congress after Kline did not show up on Tuesday for a scheduled deposition.

The committee subpoenaed Kline after one of his former subordinates told the panel that dozens of people in Trump's administration were granted security clearances despite "disqualifying issues" in their backgrounds.

Fox News' Bill Mears, Alex Pappas, Lawrence Edward, Mike Emanuel and The Associated Press contributed to this report.