WASHINGTON — The White House declared war on the House impeachment inquiry on Tuesday, announcing that it would not cooperate with what it called an illegitimate and partisan effort “to overturn the results of the 2016 election” of President Trump.

In a letter to House Democratic leaders, the White House counsel said the inquiry violated precedent and Trump’s due process rights in such an egregious way that neither he nor the executive branch would willingly provide testimony or documents, a daring move that sets the stage for a constitutional clash.

“Your unprecedented actions have left the president with no choice,” said the eight-page 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.”

The letter came hours after the White House blocked the interview of a key witness, Gordon D. Sondland, the US ambassador to the European Union, just hours before he was to appear on Capitol Hill.


Trump, defiant as investigators dig further into his efforts to pressure Ukraine to find dirt on his political rivals, ridiculed the inquiry as spurious, signaling even before the release of the top White House lawyer’s letter that he planned to stonewall Congress, an act that could itself build the case for charging him in an impeachment proceeding with obstruction.

“I would love to send Ambassador Sondland, a really good man and great American, to testify,” Trump wrote on Twitter Tuesday morning around the time Sondland was to appear, “but unfortunately he would be testifying before a totally compromised kangaroo court, where Republican’s rights have been taken away.”

Earlier on Tuesday, House Democrats said they would regard the president’s stance as obstruction. Representative Adam B. Schiff, Democrat of California and chairman of the House Intelligence Committee, said the administration’s refusal to allow Sondland to appear was “strong evidence” of “obstruction of the constitutional functions of Congress, a coequal branch of government.”


Schiff told reporters that the State Department was also withholding text messages Sondland had sent on a private device that were “deeply relevant” to the inquiry. He later indicated the House would issue a subpoena for his testimony and the messages.

“The American people have the right to know if the president is acting in their interests, in the nation’s interests with an eye toward our national security, and not in his narrow personal, political interests,” Schiff told reporters. “By preventing us from hearing from this witness and obtaining these documents, the president and secretary of state are taking actions that prevent us from getting the facts needed to protect the nation’s security.”

The decision to block Sondland from being interviewed was delivered at the last minute, after the ambassador had already flown to Washington from Europe, and lawmakers had returned from a two-week recess to observe the questioning.

Trump administration lawyers and aides have spent days puzzling over how to respond to the impeachment inquiry, and the abrupt move suggested that the president’s team has calculated that he is better off risking the House’s ire — and even an impeachment article focused on the obstruction — than setting a precedent for cooperation with an investigation they have strenuously argued is illegitimate.


The strategy, if it holds, carries substantial risk to the White House. Privately, some Republicans had urged the White House to allow witnesses like Sondland to appear, in order to deflate Democratic accusations of a coverup and offer a public rationale for the president’s actions toward Ukraine. Now, some Republicans worry, Democrats have more fodder to argue publicly that Trump has something to hide.

Schiff said the Intelligence Committee, working with both the Foreign Affairs and the Oversight and Reform panels, would continue its work regardless. But beyond issuing a subpoena for Sondland, the chairman did not detail how he might seek to crank up pressure on the White House to comply, and the standoff may create a quandary for Democrats who had hoped to move quickly in extracting crucial evidence and decide in short order whether to push forward on impeaching Trump.

House Speaker Nancy Pelosi said it was too early to know whether Democrats might draft an article of impeachment based on the obstruction issue, akin to one adopted by the House Judiciary Committee in the 1970s impeachment proceedings against Richard M. Nixon.

“The president is obstructing Congress from getting the facts that we need,” Pelosi told reporters in Seattle, where she was holding an unrelated event. “It is an abuse of power for him to act in this way.”

Sondland has become enmeshed in the burgeoning saga of how the president sought to push the Ukrainians to investigate former vice president Joe Biden, his son, and Democrats.


Although Ukraine is not in the EU, Trump instructed Sondland — a wealthy hotelier and contributor to his campaign — to take a lead in his administration’s dealings with the country.

Democrats consider him a key witness to what transpired, including whether the president sought to use a $391 million package of security assistance and the promise of a White House meeting as bargaining chips to essentially bully President Volodymyr Zelensky of Ukraine into digging up dirt on the Bidens and other Democrats.

Trump’s allies on Capitol Hill rushed to his defense on Tuesday and accused Schiff and the Democrats of running what they described as an unfair process, though they made clear they thought Sondland would have been a helpful witness for the president’s case.

“We were looking forward to hearing from Ambassador Sondland,” said Representative Jim Jordan of Ohio, the top Republican on the Oversight and Reform Committee, adding that Republicans believed Sondland would “reinforce exactly” what lawmakers and aides heard least week from Kurt D. Volker, the former US special envoy to Ukraine.

Volker told investigators he knew of nothing improper between the two countries, although he turned over a trove of documents that raised further questions.

“But we understand exactly why the administration, exactly why the State Department has chosen to say, ‘Look if it’s going to be this kind of process . . . ,’ ” Jordan added.

It was unclear what the Trump administration’s position would mean for other witnesses expected to testify in the House investigation. Marie L. Yovanovitch, the former ambassador to Ukraine, is scheduled to appear on Friday. The State Department has also missed a subpoena deadline to hand over documents the House has demanded related to Ukraine.


Sondland interacted directly with Trump, speaking with the president several times around key moments that House Democrats are now investigating, including before and after Trump’s July call with Zelensky.

The president asked Zelensky in that conversation to do him “a favor” and investigate the Bidens and matters related to 2016.

Text messages provided to Congress last week showed that Sondland and another senior diplomat had worked on language for a statement they wanted the Ukrainian president to put out in August that would have committed him to the investigations sought by Trump.

The diplomats consulted with Rudy Giuliani, Trump’s personal lawyer, about the statement, believing they needed to pacify him in order to allow the United States to normalize relations with the Ukrainians.

Sondland was also involved in a back-and-forth with top US diplomats to Ukraine over text last month that suggests some senior State Department officials believed that Trump may have been holding up the security aid as leverage for getting its leaders to conduct the investigations Trump wanted.

“As I said on the phone, I think it’s crazy to withhold security assistance for help with a political campaign,” William B. Taylor Jr., a top US official in Ukraine, wrote in one exchange in early September.

After receiving the text, Sondland called Trump, who asserted it was false.

“Bill, I believe you are incorrect about President Trump’s intentions,” Sondland wrote in the messages. “The President has been crystal clear no quid pro quo’s of any kind.”

Sondland added: “I suggest we stop the back and forth by text.”

There have been conflicting accounts of Sondland’s views, however. Senator Ron Johnson, Republican of Wisconsin, told The Wall Street Journal last week that Sondland had told him in August that the release of the aid was contingent upon Ukraine opening the investigations. Johnson said he was alarmed and asked Trump if there was a quid pro quo involved. The president adamantly denied it, he said.

Robert D. Luskin, Sondland’s lawyer, said in a statement that as a State Department employee, his client had no choice but to comply with the administration’s direction. He said Sondland was “profoundly disappointed” he was not able to testify, and would do so in the future if allowed.