Nancy Pelosi has made a blistering reply to the White House after it asserted that it would not comply with the House's impeachment inquiry, with the House Speaker telling the president, "you are not above the law."

On Tuesday, the White House said in a letter to members of Congress that it was refusing to cooperate with the impeachment inquiry, calling it "unconstitutional" and denying the requests for testimony and documents. As The New York Times noted, a letter from White House counsel Pat A. Cipollone came hours after the White House blocked testimony from U.S. Ambassador Gordon Sondland, a key witness whose text messages with another U.S. diplomat appeared to spell out a quid pro quo from Donald Trump to Ukraine as he sought to have that country dig up dirt on Joe Biden.

In her response to the letter, Pelosi took direct aim at Trump and what she saw as his lawlessness.

"For a while, the President has tried to normalize lawlessness. Now, he is trying to make lawlessness a virtue," Pelosi said in a letter responding to the White House. "The American people have already heard the President's own words – 'do us a favor, though.' The President's actions threaten our national security, violate our Constitution and undermine the integrity of our elections. The White House letter is only the latest attempt to cover up his betrayal of our democracy, and to insist that the President is above the law."

Pelosi added that the White House letter was "manifestly wrong," echoing the statements from constitutional experts who noted there is no requirement to hold a vote on an impeachment inquiry, as Trump and his allies have claimed. This step has been taken in past impeachments, though there it is not required in the U.S. Constitution.

Pelosi's letter comes as tensions between the White House and House committees have risen. Democrats in Congress launched an impeachment inquiry after a whistleblower issued a complaint that Trump was trying to press Ukraine into digging up dirt on Joe Biden and his son, Hunter Biden. Trump has claimed repeatedly that he did nothing wrong in regard to Ukraine, even as the White House released a summary of a phone call between Trump and the Ukrainian president that showed Trump pressing him to investigate Biden.

Pelosi had been famously hesitant to move forward on impeachment after the final Russia report outlined Trump's attempts to obstruct the investigation --- drawing criticism from many members of her own party --- but now has been aggressive in going after Trump in the current impeachment inquiry. In her statement on Tuesday, Pelosi issued a clear warning to Trump.

"Mr. President, you are not above the law," Pelosi wrote. " You will be held accountable."