US President Donald Trump speaks to reporters before leaving the White House in Washington D.C. Sept. 12, 2019. (Photo by Ting Shen/Xinhua)

A defiant White House declared war on Tuesday against the impeachment investigation of President Donald Trump, blasting the process as partisan, illegitimate and unconstitutional and saying neither the president nor his administration will cooperate.

In a fiery letter, the White House threw down the gauntlet to House Speaker Nancy Pelosi and the chairmen of three congressional panels leading the inquiry, challenging them to proceed with their effort to oust Trump despite zero future cooperation.

"Put simply, you seek to overturn the results of the 2016 election and deprive the American people of the president they have freely chosen," White House counsel Pat Cipollone wrote in an eight-page letter.

"Your inquiry lacks any legitimate constitutional foundation, any pretense of fairness, or even the most elementary due process protections," he said of the probe, which is weighing whether Trump abused his office by seeking a corruption probe in Ukraine of his rival Joe Biden.

"President Trump cannot permit his administration to participate in this partisan inquiry under these ­circumstances."

Pelosi fired back, terming the letter "manifestly wrong" and describing it as "another unlawful attempt to hide the facts."

"Mr President, you are not above the law. You will be held accountable," she said, warning that "continued efforts to hide the truth of the president's abuse of power from the American people will be regarded as further evidence of obstruction."

The standoff set Washington on a path toward a constitutional crisis and into unknown territory, with the potential for a court showdown just as the nation gears up for the 2020 election.

The White House's chief objection was the fact the House of Representatives had not held a formal vote to launch the inquiry.

Democrats say it is not needed because the impeachment process is in its earliest stages, equivalent to gathering evidence for an indictment.

Only afterward would the Democrats call a vote. If a majority of House members back impeachment, the matter shifts to a trial in the Senate, currently controlled by Republicans.

Top Senate Republican Mitch McConnell expressed support for Trump's strategy, tweeting that the House had failed "to follow the same basic procedures that it has followed for every other President in our history."

The White House letter capped a day of explosive developments that included Trump barring a key witness, Ambassador to the European Union Gordon Sondland, from speaking to Congress - calling it a "totally compromised kangaroo court."


Newspaper headline: WH rules out House cooperation