WASHINGTON – House investigators released numerous text messages late Thursday night illustrating how senior State Department officials coordinated with the Ukrainian president’s top aide and President Donald Trump’s personal lawyer to leverage a potential summit between the heads of state on a promise from the Ukrainians to investigate the 2016 U.S. election and an energy company that employed the son of 2020 Democratic candidate Joe Biden.

The texts, which former special U.S. envoy to Ukraine Kurt Volker provided investigators during a nearly 10-hour deposition Thursday, reveal that officials felt Trump would not agree to meet with Ukrainian President Volodymyr Zelensky unless Zelensky promised to launch the investigations – and did so publicly. Though the texts do not mention Biden by name, congressional Democrats leading an impeachment inquiry are pointing to them as clear evidence that Trump conditioned normal bilateral relations with Ukraine on that country first agreeing “to launch politically motivated investigations,” top Democrats said in statement Thursday night.

“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,” Volker texted Zelensky’s aide, Andrey Yermak, on July 25, hours before Trump and the Ukrainian president spoke via phone. The transcript of that conversation was released by the White House last week.

Yet two weeks after that call the president still had not agreed to meet with Zelensky – and administration officials sought to convince the Ukrainians that Trump would need a public pledge before agreeing to the meeting, according to the text messages.

“I think potus really wants the deliverable,” U.S. ambassador to the European Union Gordon Sondland texted to Volker on Aug. 9, noting that Zelensky might give a news conference announcing his intent to investigate. “To avoid misunderstandings, might be helpful to ask Andrey for a draft statement (embargoed) so that we can see exactly what they propose to cover.”

By the next day, the Ukrainians had agreed to announce their plans to carry out Trump’s investigations alongside the date for a meeting between the two heads of state, the messages indicate.

“Once we have a date, 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,” Yermak texted Volker on Aug. 10. Hunter Biden, the former vice president’s son, sat on the board of Burisma for five years.

But Trump never committed to a meeting. And as the United States resisted giving Zelensky an audience with Trump, administration officials’ discussions suggest the White House was issuing an escalating series of demands.

“Are we now saying that security assistance and WH meeting are conditioned on investigations?” U.S. charges d’affaires in Ukraine William B. “Bill” Taylor texted to Sondland on Sept. 1, after Trump skipped a trip to Poland where he was meant to visit with Zelensky. Sondland swiftly moved the conversation from text messages to a phone call.

“As I said on the phone, I think it’s crazy to withhold security assistance for help with a political campaign,” Taylor later texted Sondland on Sept. 9, complaining that the Trump administration’s decision to withhold congressionally approved military aid to Ukraine had already created a “nightmare scenario.”

“The president has been crystal clear no quid pro quo’s of any kind,” Sondland replied. “The president is trying to evaluate whether Ukraine is truly going to adopt the transparency and reforms that president zelensky promised during his campaign I suggest we stop the back and forth by text.”

Sondland declined to comment through an attorney, Jim McDermott. Volker did not respond to requests for comment. The State Department did not immediately respond to messages, nor did the White House.

The abrupt end to the texts mirrors the current political climate on Capitol Hill, where Democrats and Republicans are fiercely divided over whether Trump’s efforts to pressure Zelensky into investigating Burisma and the 2016 elections were proper diplomacy or an abuse of power.

House Intelligence Committee member Rep. Eric Swalwell, D-Calif., told reporters Thursday that Volker had provided “ample evidence” to show that it was a “requirement” that Zelensky launch the 2016 elections investigation to “exonerate Russia’s role,” and that the focus on Burisma was to investigate Biden. “That was an understood predicate for the meeting,” Swalwell said.

But House Republicans emerged from Volker’s day-long deposition saying that nothing Volker had said damaged the president and that there was no proof Trump had sought a quid pro quo. Rep. Jim Jordan, R-Ohio, one of Trump’s most aggressive defenders, said on Twitter that “the facts we learned today from Ambassador Volker undercut the salacious narrative that @RepAdamSchiff is using to sell his impeachment ambitions.”

Schiff, a California Democrat, is chairman of the House Intelligence Committee and leading the impeachment inquiry.

Volker is the first of several State Department officials expected to give congressional investigators an inside account of the Trump administration’s efforts to press for a Ukrainian investigation of Biden, who as a leading 2020 Democratic candidate to challenge Trump for the White House has become a fixed target of the president’s attacks.

At the heart of Trump’s effort is the contention of his lawyer, Rudy Giuliani, that as vice president, Biden pushed for the firing of Ukraine’s then-prosector general, Viktor Shokin, as part of a corrupt plot to halt investigations of Burisma.

Volker told House investigators on Thursday that he had warned Giuliani against trusting the information he was receiving from Ukrainian political figures about Joe Biden and his son. He said he tried to caution Giuliani that his Ukrainian sources were unreliable and that he should be careful about putting faith in their theories, according to people who spoke on the condition of anonymity to discuss the closed-door meeting.

But the texts show that Volker also introduced Giuliani to Yermak, so that the two could speak on July 22, and better facilitate direct contacts between Trump and Zelensky.

Zelensky was “sensitive about Ukraine being taken seriously, not merely as an instrument in Washington domestic, reelection politics,” Taylor had texted Sondland on July 21. Sondland replied that he was more “worried about the alternative” if Trump and Zelensky did not speak to “get the conversation started and the relationship built.”

“Most impt is for Zelensky to say that he will help the investigation,” Volker had informed Sondland on July 19, according to the text messages.

Giuliani had been “advocating” for Trump and Zelensky to speak by phone on July 25, Volker’s texts show. In an interview Thursday night, Giuliani said he also knew of conversations between U.S. and Ukrainian officials about a statement that would commit the Ukrainian president to investigate Burisma. But he insisted that “to my knowledge, it was never put out.”

Giuliani also said that he “did not recall” ever being told by Volker that his claims were spurious. “I’m pretty certain he never said that the claims weren’t true because I would have jumped all over him and asked him what kind of investigation he’d done and how he knew that,” Giuliani said of Volker.

Joe Biden and his defenders have denied Giuliani’s accusations and noted that Biden’s push to remove Shokin, Ukraine’s former prosecutor general, was part of a broader international effort that included the European Union and the International Monetary Fund, where leaders viewed Shokin as inept.

Volker also told lawmakers Thursday that he and other State Department officials cautioned the Ukrainians to steer clear of U.S. politics. Getting involved, he said he told them, would open the nation to allegations that it was interfering in an American election and could be detrimental to Ukraine long-term, according to the people familiar with his testimony.

House investigators asked Volker whether efforts to pressure the Ukrainians included withholding a leader-level meeting with Zelensky and about $400 million in military aid from the country, those familiar with the meeting said.

Volker acknowledged, these people said, that the Trump administration had extended an invitation to Zelensky shortly after his election in the spring and that it was later withdrawn. Volker told House investigators that Trump’s delay in meeting Zelensky and the decision to halt military aid deeply concerned Ukrainian officials, who view Washington as a critical ally against Russia, the people familiar with his testimony said.

Volker said Thursday that he was never given an explanation about the aid suspension.

Volker started his job at the State Department in 2017 in an unusual part-time arrangement that allowed him to continue consulting at BGR, a powerful lobbying firm that represents Ukraine and the U.S.-based defense firm Raytheon. During his tenure, Volker advocated for the United States to send Raytheon-manufactured antitank Javelin missiles to Ukraine – a decision that made Raytheon millions of dollars. BGR has said Volker recused himself from all Ukraine-related matters in response to criticisms about conflicts of interest.

On Thursday afternoon, the State Department announced that it had approved the sale of 150 additional Javelin missiles to Ukraine for up to $39.2 million and notified Congress.

Volker also kept his job as executive director of the McCain Institute, an affiliation that may explain why Volker never penetrated Trump’s inner circle, given the president’s open disdain for Sen. John McCain, R-Ariz., who died last year.

Previously, he served as the U.S. ambassador to NATO during the George W. Bush administration.