Never-before-heard audio, obtained exclusively by CNN, shows how former U.S. President Donald Trump's longtime adviser Rudy Giuliani pressured the Ukrainian government in 2019 to investigate baseless allegations about then-candidate Joe Biden.

The audio is of a July 2019 phone call between Giuliani, U.S. diplomat Kurt Volker, and Andriy Yermak, a senior adviser to Ukrainian President Volodymyr Zelensky. The call was a precursor to Trump's infamous call with Zelensky, and both conversations later became a central part of Trump's first impeachment, where he was accused of soliciting Ukrainian help for his campaign.

During the roughly 40-minute call, Giuliani repeatedly told Yermak that Zelensky should publicly announce investigations into possible corruption by Biden in Ukraine, and into claims that Ukraine meddled in the 2016 election to hurt Trump. (These separate claims are both untrue.)

"All we need from the President [Zelensky] is to say, I'm gonna put an honest prosecutor in charge, he's gonna investigate and dig up the evidence, that presently exists and is there any other evidence about involvement of the 2016 election, and then the Biden thing has to be run out," Giuliani said, according to the audio. "... Somebody in Ukraine's gotta take that seriously."

The new audio demonstrates how Giuliani aggressively cajoled the Ukrainians to do Trump's bidding. And it undermines Trump's oft-repeated assertion that "there was no quid pro quo" where Zelensky could secure US government support if he did political favors for Trump.

The call was one of the opening salvos in the years-long quest by Trump and his allies to damage Biden and subvert the 2020 election process -- by soliciting foreign meddling, lying about voter fraud, attempting to overturn the results, and inciting the deadly January 6 assault on the Capitol.

There is an ongoing criminal investigation into Giuliani and his Ukraine dealings, including whether he violated lobbying laws while coordinating with ex-officials who gave him dirt on the Bidens. The federal inquiry ramped up when the FBI raided Giuliani's home and office in late April. It's unclear if the call with Yermak is part of the investigation. Giuliani denies all wrongdoing.

A partial transcript of the Giuliani-Yermak phone call was first published by BuzzFeed News in April, and Time Magazine was first to publish some key excerpts from the call in February.

Over and over, Giuliani pressed for the investigations, according to the audio recording. Giuliani even said the US-Ukraine diplomatic relationship would improve if Zelensky launched the probes. Giuliani and Volker suggested during the call that a public announcement could clear the way for Zelensky's much-desired visit to the US, or for in-person meetings with Giuliani.

"That would clear the air really well," Giuliani said, according to the recording. "And I think it would make it possible for me to come and make it possible, I think, for me to talk to the President (Trump) to see what I can do about making sure that whatever misunderstandings are put aside ... I kinda think that this could be a good thing for having a much better relationship."

The tape provides a firsthand perspective to one of the most consequential moments of Trump's presidency. The Ukrainians are occasionally heard shuffling through papers, and the phone that's dialed into the call rings a few times during the conversation -- but Yermak stays on the line with Giuliani.

Giuliani did not respond to CNN's requests to comment about the new audiotape. In the past, he has said he didn't do anything wrong in Ukraine and was merely pursuing his client's best interests. (He was Trump's personal lawyer at the time.) Giuliani also condemned Trump's impeachment over the Ukraine affair and said Trump's conduct was constitutional and proper.

CAJOLING AND ARM-TWSITING

The call was a big moment for Giuliani's quest to damage Biden's candidacy.

The former New York City mayor had spent months meeting with Ukrainians to find dirt on the Biden family, and to corroborate right-wing conspiracies that anti-Trump forces in Ukraine undermined his 2016 campaign. Giuliani met with officials who weren't considered trustworthy by US diplomats in Ukraine, including Volker -- but they told Giuliani what he wanted to hear.

Zelensky, who was a comedian and actor before entering politics, was sworn in as Ukraine's president in May 2019. Giuliani sounded eager to connect with the new president and his team.

Several weeks later, Volker brokered a call between Giuliani and Yermak, who is a longtime friend and adviser to Zelensky. This was Giuliani's first opportunity to make his pitch about the Biden investigation to Zelensky's inner circle, which was desperate to get to know Trump's team and to firm up US military support for Ukraine's ongoing war against Russian proxies in the east.

The call started with Giuliani explaining several convoluted right-wing conspiracy theories about Biden's diplomatic dealings in Ukraine and supposed Ukrainian meddling in the 2016 election.

Giuliani pushed many of these theories even after Volker had warned him that the Ukrainian officials who were feeding him information were not trustworthy, and said the corruption claims against Biden were "simply not credible," according to Volker's testimony in the House impeachment inquiry.

"I got information from a reliable investigator, international investigator, that there was a certain amount of activity in Ukraine during the 2016 election," Giuliani said to Yermak during the call, pushing the false claim that US embassy officials tried to "produce dirt on then-candidate Trump and Paul Manafort."

"Another one was involved with (George) Soros ... Soros apparently is behind a lot of this," Giuliani said, referring to the liberal billionaire philanthropist who is the subject of many GOP conspiracies.

Giuliani also brought up the false claim that Biden acted corruptly as vice president when he urged Zelensky's predecessor, Petro Poroshenko, to fire the country's top prosecutor in 2016. (Multiple witnesses in the impeachment inquiry testified that Biden was simply following bipartisan US policy, and that the Ukrainian prosecutor needed to go because he was corrupt.)

"To me, as a lawyer, it sounds like a bribe," Giuliani said. "A bribe is offering something of value in exchange for official action. So, he offered Poroshenko a $1.2 billion loan guarantee, critical to Poroshenko's success as president, in exchange for getting rid of a prosecutor general."

He peppered in several disclaimers throughout the conversation, like saying he wasn't sure if the corruption claims against Biden were true and that he only wants "the truth" to come out. Giuliani also told Yermak, "I'm not telling (Zelensky) what to say," even though he very clearly said on a few occasions that Zelensky should announce the specific probes that Trump wanted.

One of the Ukrainians who was listening into the phone call, ex-Zelensky adviser Igor Novikov, told CNN last month that Giuliani's antics threatened Ukraine's already-fragile national security situation.

"We're a country fighting an active war with Russia for many years," he said. "So, anything to do with swapping favors within our bilateral relationship in exchange for trying to get us involved in US domestic politics is just wrong, on many levels, morally, ethically and probably even legally."

'THAT WOULD BE GOOD FOR ALL OF US'

During the call, Yermak listened patiently and tried to reroute the conversation to official diplomatic matters, like arranging dates for Zelensky to make his first official visit to the US. But he also gave signals to the Americans on the line that he'd work to move the ball forward on the "investigations."

"I'm absolutely sure that as soon as the dates of the President Zelensky's upcoming visit to United States will be confirmed, I am ready to be personally assume control of the preparation," Yermak said. "And of course, I will be ready to come, and we can (be) personally sitting (down), and in detail discuss all the questions, all this investigation which you listed in our conversation."

The tone from the Americans changed -- Giuliani and Volker liked what they were hearing. And Volker mentioned that Trump was scheduled to speak with Zelensky soon and congratulate him on his major parliamentary victory.

By the end of the call, it seemed clear to Yermak what needed to happen to get on Trump's good side.

"I'm sure that Zelensky will say that," Yermak said, referring to the requests from Giuliani and Volker that Zelensky should mention the investigations during his upcoming call with Trump.

"Good," Volker said.

"Believe me, Andriy, that would be good for all of us," Giuliani replied. "That would move it along very fast. And I can assure you that, as far as I'm concerned, I think they should talk this week."

Volker said, "I will press that as well," referring to getting Trump to call Zelensky.

Trump connected with Zelensky three days later, on July 25, 2019. According to a rough transcript released by the White House, Trump raised with Zelensky some of the same baseless theories that Giuliani mentioned to Yermak. Trump said, "I would like you to do us a favor" and investigate the allegations.

His conduct during that now-infamous phone call with Zelensky led to a whistleblower complaint from a US intelligence official who claimed Trump abused his powers and solicited foreign help in the 2020 election from Ukraine. The scheme unraveled within a few months, and Trump was impeached by the House of Representatives. He would be acquitted after a Senate trial.