The White House has indicated it will not cooperate with the impeachment inquiry into Donald Trump, calling the investigation both "illegitimate and unconstitutional."

In an eight-page letter addressed to House Speaker Nancy Pelosi and other top Democrats, White House counsel Pat Cipollone states the Trump administration will not comply with demands for testimony and documents pertaining to Trump's dealings with foreign leaders—specifically his interactions with Ukranian President Volodymyr Zelensky.

"Your unprecedented actions have left the President with no choice," reads the letter, obtained the Los Angeles Times. "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."

House Democrats have issued a number of subpoenas concerning POTUS' alleged efforts to extort the Ukrainian government into producing dirt on his political rival Joe Biden. Following reports of a whistleblower complaint, the White House released a rough transcript of a July 25 phone call in which Trump asked Zelensky to "look into" Joe Biden and his son Hunter Biden, who took a position at a Ukranian energy company while his father was serving as vice president. It's also important to note that Trump withheld U.S. military aid to Ukraine a week before the phone call in questions. This, of course, raised questions about the president's motivations, as well as accusations that Trump offered Zelensky a quid pro quo.

Trump has denied the allegations, insisting his phone call with the Ukranian president was "absolutely perfect" and "totally appropriate." The Trump administration has continued to dismiss the impeachment inquiry as a Democratic ploy to influence the 2020 election.

"Many Democrats now apparently view impeachment not only as a means to undo the democratic results of the last election, but as a strategy to influence the next election, which is barely more than a year away," the letter reads. "As one member of Congress explained, he is 'concerned that if we don't impeach the President, he will get reelected.' Your highly partisan and unconstitutional effort threatens grave and lasting damage to our democratic institutions, to our system of free elections, and to the American people."

The White House letter was sent to Congressional Democrats shortly after Trump blocked the testimony of Gordon Sondland, the U.S. ambassador to the European Union. Lawmakers issued a subpoena for Sondland, requesting testimony and documents related to his involvement in the Ukraine controversy. 

House Intelligence Committee Chairman Adam Schiff said Ambassador Sondland has text messages or emails on his person device related to the matter, and that the State Department is withholding those documents.

"The failure to produce this witness, the failure to produce these documents, we consider...additional strong evidence of obstruction of the constitutional functions of Congress," Schiff said. "The American people have a right to know if President Trump is working for their interests or in his own political interests."

Sondland's attorney, Robert Luskin, said his client was "profoundly disappointed" that he did not get the chance to testify Tuesday.

"Ambassador Sondland had previously agreed to appear voluntarily today, without the need for a subpoena, in order to answer the Committee’s questions on an expedited basis," Luskin said in a statement to NBC News. "As the sitting U.S. Ambassador to the E.U. and employee of the State Department, Ambassador Sondland is required to follow the Department’s direction.... Ambassador Sondland believes strongly that he acted at all times in the best interests of the United States, and he stands ready to answer the Committee’s questions fully and truthfully."