In a letter to House Democratic leaders, the White House said the inquiry had violated precedent and denied President Trump's due process rights in such an egregious way that neither he nor the executive branch would willingly provide testimony or documents.

"Your unprecedented actions have left the president with no choice," said the letter signed by Pat A. Cipollone, the White House counsel. "In order to fulfill his duties to the American people, the Constitution, the executive branch and all future occupants of the office of the presidency, President Trump and his administration cannot participate in your partisan and unconstitutional inquiry under these circumstances."

But in refusing to cooperate with what Mr. Trump on Tuesday called a "kangaroo court," the president risked ensuring the very outcome he would rather avoid. House Democrats made clear that his failure to comply with their demands for information could form the basis for its own article of impeachment.