The Democratic chairmen of three House committees investigating President Trump released dozens of text messages Thursday from top State Department officials which they say show the White House sought to tie aid to Ukraine with a promise from Kyiv to launch investigations that might benefit President Trump's reelection campaign.

Reps. Adam Schiff, Elijah Cummings and Eliot Engel released text messages provided by Kurt Volker, the former U.S. special envoy to Ukraine who spent more than nine hours on Thursday testifying behind closed doors as the inquiry's first official witness.

"Based on the first production of materials, it has become immediately apparent why Secretary [of State Mike] Pompeo tried to block these officials from providing information," the chairmen wrote Thursday in a letter to their colleagues on the House Intelligence, Oversight and Reform and Foreign Affairs Committees.

"Earlier today, selected portions of these texts were leaked to the press out of context," they wrote. "In order to help correct the public record, we are now providing an attachment with more complete excerpts from the exchanges. The additional excerpts we are providing are still only a subset of the full body of materials, which we hope to make public after a review for personally identifiable information."

The letter did not indicate whether the partial release of text messages was representative of the complete texts in possession of the committees.

The White House did not immediately respond, but earlier Trump tweeted: "As the President of the United States, I have an absolute right, perhaps even a duty, to investigate, or have investigated, CORRUPTION, and that would include asking, or suggesting, other Countries to help us out!"

The series of text exchanges cover a period from July 19 to September 9 and discuss dates and conditions for a White House visit by Ukraine's president, Volodymyr Zelenskiy.

Officials taking part are Volker; William Taylor, who as interim chargé d'affaires in Kyiv is the top U.S. diplomat in Ukraine; Gordon Sondland, U.S. ambassador to the European Union; and Andrey Yermak, a top aide to Zelenskiy. In some of the exchanges, Trump's personal attorney, former New York Mayor Rudolph Giuliani, also participates.

In one exchange dated Sept. 9, in a text from Taylor to Sondland, the career diplomat says, "I think it's crazy to withhold security assistance for help with a political campaign."

Sondland responds: "Bill, I believe you are incorrect about President Trump's intentions. The President has been crystal clear no quid pro quo's of any kind."

Sondland continues, "I suggest we stop the back and forth by text."

Volker resigned last week after being named in a whistleblower complaint alleging that the White House pressured Zelenskiy to investigate former vice president and Democratic presidential candidate Joe Biden's son, Hunter. Hunter Biden held a seat on the board of Burisma, a prominent Ukrainian energy company, while his father led U.S. policy on Ukraine in the Obama administration. Trump has asserted without evidence that Hunter's relationship with the company was unlawful.

In a rough transcript of a July 25 telephone call between Trump and Zelenskiy, Trump asks as a "favor" from the Ukrainian president that he undertake an investigation of Biden. Trump also mentions a discredited conspiracy theory involving Ukraine and interference in the 2016 presidential election.

On July 19, in discussions about the upcoming call, Volker texts Sondland: "Most impt is for Zelensky to say that he will help investigation."

On July 21, Taylor — who served as ambassador to Ukraine under President George W. Bush and was appointed interim chargé d'affaires in June after the recall of Ambassador Marie Yovanovitch — cautions Sondland that Zelensky "is sensitive about Ukraine being taken seriously, not merely as an instrument in Washington domestic, reelection politics."

Sondland replies that they need to proceed with establishing a relationship "irrespective of the pretext."

Sondland, a hotel developer with no previous diplomatic experience, donated $1 million to Trump's inaugural committee, according to the non-partisan Center for Responsive Politics. He was nominated to be EU ambassador by the president in 2018 and approved by the Senate on a bipartisan vote.

In a July 25 message between Volker and Yermak that occurred just ahead of the Trump-Zelenskiy call, Volker writes: "Heard from White House—assuming President Z convinces trump he will investigate/'get to the bottom of what happened' in 2016, we will nail down date for visit to Washington."

Weeks later, on Aug. 9, Sondland and Volker exchange texts as they try to establish a date for Zelenskiy's visit:

Sondland: Morrison ready to get dates as soon as Yermak confirms.

Volker: Excellent!! How did you sway him? :)

Sondland: Not sure i did. I think potus really wants the deliverable

The next day, in an exchange between Yermak and Volker, Yermak writes that when a date for a visit is established, he "will call for a press briefing, announcing upcoming visit and outlining vision for the reboot of US-UKRAINE relationship, including among other things Burisma and election meddling in investigations"

On Aug. 13, Volker sends Sondland what appears to be a proposed draft of a Ukraine statement in which Kyiv pledges to pay "special attention" to U.S. election interference, "especially with the alleged involvement of some Ukrainian politicians." In the proposed draft, Kyiv would further agree to investigate "Burisma and the 2016 U.S. elections ..."

"The alleged involvement of some Ukrainian politicians" in U.S. elections appears to be a reference to a discredited conspiracy theory that Ukraine, not Russia, meddled in the 2016 presidential election.

Sondland replies: "Perfect. Lets send to Andrey after our call."

On Aug. 17, Sondland asks Volker: "Do we still want Ze to give us an unequivocal draft with 2016 and Boresma?"

Volker: "That's the clear message so far ..."

In an exchange on Aug. 29, Yermak texts Volker, "Need to talk with you," and then sends a link to a Politico story headlined "Trump holds up Ukraine military aid meant to confront Russia."

On Sept. 1, Taylor, apparently seeking clarification on the Trump-Zelenskiy meeting in Washington, texts Sondland: "Are we now saying that security assistance and WH meeting are conditioned on investigations?"

Sondland replies: "Call me."

A week later, Taylor writes to Volker: "The nightmare is they give the interview and don't get the security assistance. The Russians love it. (And I quit.)"

The next day, Taylor writes to Sondland: "The message to the Ukrainians (and Russians) we send with the decision on security assistance is key. With the hold, we have already shaken their faith in us. Thus my nightmare scenario."

Taylor: "Counting on you to be right about this interview, Gordon."

Sondland: "Bill, I never said I was 'right'. I said we are where we are and believe we have identified the best pathway forward. Lets hope it works."

What follows is the exchange in which Taylor says it's "crazy" to withhold security assistance and Sondland tries to assure Taylor there's no quid pro quo.

At the end of the exchange, Sondland advises "I suggest we stop the back and forth by text ..."

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