President Trump unleashed a torrent of criticisms on Democratic leaders in a series of tweets and televised appearances Wednesday as House leaders stepped up their impeachment inquiry into his dealings with Ukraine.

The profane and personal attacks punctuated the day as it became clear that Democratic leaders are moving quickly with their investigation.

On Wednesday, House Democrats promised to subpoena the White House by the end of the week if officials refuse to produce documents related to Trump’s July phone call with Ukraine’s president and other efforts to persuade the country’s new leader to investigate Trump’s political rival Joe Biden. Additionally, lawmakers will hold interviews in coming days with people they deem key witnesses in their investigation, including Trump’s former envoy for Ukraine, the intelligence community’s inspector general and the ousted ambassador to Kiev.

Secretary of State Mike Pompeo said Oct. 2 he was on the call in which President Trump pressed Ukraine's leader to investigate former vice president Joe Biden. (The Washington Post)

“We’re not fooling around here,” House Intelligence Chairman Adam B. Schiff said as he appeared with House Speaker Nancy Pelosi (D-Calif.) at a news conference on Capitol Hill. “We don’t want this to drag on months and months and months.”

The president, on Twitter, accused Pelosi of “wasting everyone’s time and energy on BULLSHIT.” Later, during two televised appearances alongside the president of Finland, Trump laid into Schiff, calling him a ­“lowlife” and a “shifty, dishonest guy” as the Finnish leader looked on uncomfortably. He attacked Schiff for presenting an exaggerated version of the phone call during a hearing last week. Schiff defended his account as obvious parody.

While the impeachment inquiry is centered on the president, his top aides are increasingly becoming swept up in the controversy. Earlier in the day, Secretary of State Mike Pompeo confirmed that he listened in on Trump’s call with Ukrainian President Volo­dymyr Zelensky and reiterated his complaint from the day before that Democrats’ demands for interviews with State Department officials amounted to an act of intimidation.

Rep. Jamie Raskin (D-Md.) revealed documents on Oct. 2 that had been provided to Congress by the State Department inspector general. (The Washington Post)

“We won’t tolerate folks on Capitol Hill bullying and intimidating State Department employees — that’s unacceptable,” Pompeo said during a news conference in Italy.

Democrats, meanwhile, questioned the extent of Pompeo’s knowledge about the Zelensky call and warned him not to obstruct their efforts to speak with State Department officials.

Schiff said he is “deeply concerned about Secretary Pompeo’s effort now to potentially interfere with witnesses whose testimony is needed before our committee.” The top Democrat on the Senate Foreign Relations Committee, Robert Menendez (N.J.), called on Pompeo to recuse himself from all Ukraine-related matters.

Trump defended his secretary of state, noting his high marks at Harvard and the U.S. Military Academy at West Point. “Adam B. Schiff should only be so lucky to have the brains, honor and strength of Secretary of State Mike Pompeo,” Trump tweeted.

Schiff “couldn’t carry his blank strap,” Trump said in the Oval Office, omitting the word “jock” in an apparent effort to censor the schoolyard taunt.

Pompeo’s recently departed special envoy to Ukraine, Kurt Volker, is scheduled to meet with congressional investigators behind closed doors on Thursday. It remains unclear whether a transcript of the interview will be made public.

In advance of the appearance, Volker has turned over a number of documents to congressional staffers consisting of text messages with Trump’s personal attorney Rudolph W. Giuliani and other people, said a person familiar with the matter who spoke on the condition of anonymity because they were not authorized to speak on the record.

Giuliani, who was a leading figure in pushing the Ukrainian government to investigate Biden and pushing for the removal earlier this year of the U.S. ambassador to Ukraine, has insisted he was on a mission for the State Department.

According to a rough transcript of Trump’s call, Zelensky expressed appreciation for U.S. help in defending Ukraine against Russia and said he wanted to buy more U.S. weapons. Trump froze hundreds of millions of dollars in military aid to Ukraine days before the call. He replied to Zelensky, “I would like you to do us a favor though,” and requested that he investigate allegations that Democrats conspired with Ukrainians to influence the 2016 U.S. presidential election. Elsewhere in the call, Trump also pressed for an investigation into Biden and the former vice president’s son.

A whistleblower complaint, filed in August with the intelligence community’s inspector general, alleges that Trump’s call with Zelensky, along with other U.S. officials’ interactions with the Ukrainian government, reveal that Trump abused his office to pressure a foreign country to damage a political opponent in the 2020 election. The White House denies the accusation, saying Trump withheld military aid to Ukraine out of frustration over Europe’s lack of monetary support for Ukraine and continued problems related to corruption in the country.

When asked Wednesday whether he thought anything was improper on the phone call, Pompeo said that everything the Trump administration has done related to Ukraine has been ­“remarkably consistent” and focused on confronting the “threat that Russia poses” and rooting out “corruption” in Ukraine.

Many State Department employees feel that they are caught in the middle of a political battle between the agency and House committees, said a U.S. diplomat, speaking on the condition of anonymity to comment frankly about the adverse impact on morale.

Career Foreign Service officers are expected to follow the direction of State Department leadership and respond to congressional requests. It may not be possible to do both now.

“People are not politicized, and they’re very anxious not to be,” the diplomat said. “They want to do their jobs, serve their country and not be pulled into this.”

The Democrats’ quest for answers took a bizarre turn on Wednesday after State Department Inspector General Steve Linick provided lawmakers a packet of documents containing conspiracy theories and other unproven claims about Biden, his son and former U.S. ambassador to Ukraine Marie Yovanovitch, whom Trump criticized in his phone call with Zelensky.

The packet was discovered in the State Department and featured what appeared to be amateurish calligraphy intended to indicate that it’s a White House document, said people briefed on lawmakers’ meeting with Linick.

“It’s essentially a packet of propaganda and disinformation spreading conspiracy theories,” Rep. Jamie B. Raskin (D-Md.) told reporters afterward.

On Wednesday night, Giuliani told “CNN Today” that he was responsible for sending some of the materials in the packet to the State Department, saying he sent an “outline” of allegations against Biden and Yovanovitch.

In a statement, top House Democrats criticized the packet, saying these documents “reinforce concern that the president and his allies sought to use the machinery of the State Department to further the president’s personal political interests.”

The meeting with Linick had been anticipated as a potential avenue for independently gathering documents, but it proved a disappointment to some.

Raskin called the packet a “completely irrelevant distraction.”

During Wednesday’s news conference with the Finnish president, Trump refused to say exactly what he wanted from the Ukrainian president regarding Joe Biden and his son Hunter.

Trump ignored the question posed by a reporter and focused his answer instead on why he held back military aid to Ukraine, citing, as he has in the past, corruption there and the claim that the United States is the “only one who gives the big money to Ukraine.”

When the reporter pressed Trump to answer his question about the Bidens, Trump became angry and demanded that the reporter “not be rude” and instead ask a question of the Finnish president. Trump eventually said that “Biden and his son are stone-cold crooked,” then leveled his oft-made attack against the “fake news” media.

Earlier in the day, Trump continued his criticisms of the whistleblower and said his identity should become public.

“This country has to find out who that person was because that person’s a spy, in my opinion,” Trump told reporters.

The whistleblower said his complaint was based on conversations with more than half a dozen U.S. officials.

In his remarks Wednesday, Trump acknowledged that there is value in protecting the identity of whistleblowers in some cases.

“I think a whistleblower should be protected if the whistleblower’s legitimate,” he said.

Rachael Bade, Karoun Demirjian, Karen DeYoung, Colby Itkowitz, Carol Morello and Felicia Sonmez contributed to this report.