Washington (CNN) The former US special envoy for Ukraine told House investigators that he urged Ukraine's leadership not to interfere in US politics in a conversation that followed the phone call between President Donald Trump and Ukraine's Volodymyr Zelensky, according to two sources familiar with the testimony.

Volker appeared Thursday before three committees that are investigating allegations made by a whistleblower that the President sought Ukraine's assistance digging up dirt on his political rival and then the White House tried to cover it up.

In the interview, Volker told lawmakers that the Ukrainian government had a lot of questions about why the military aid was being held up and he did not have a good explanation, according to the sources describing the testimony.

Volker also testified that the Ukrainian government was concerned that a meeting with the Ukrainians and Trump was being put on hold but did not understand the reason.

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The meeting was important to Zelensky, who pushed to come to Washington on the July 25 call. According to the rough transcript, the President responds first that he will have Attorney General William Barr and Rudy Giuliani get in touch and then says: "Whenever you would like to come to the White House, feel free to call. Give us a date and we'll work that out. I look forward to seeing you."

But the meeting never happened. A planned meeting in Poland ended up being scrubbed because the President stayed in the United States to deal with a hurricane and he sent Vice President Mike Pence in his place.

Volker also told congressional investigators that he raised concerns with Giuliani about using former Ukrainian prosecutor Yuriy Lutsenko as a source for information about the Bidens and other controversies, warning that Lutsenko was not credible.

Volker, who resigned one day after he was named in the release of the whistleblower report last week alleging Trump was using the power of the presidency to ask Ukraine to investigate the Bidens for political gain in the 2020 election. Trump has denied any wrongdoing.

Republicans, however, said that Volker's testimony did not provide any evidence to support the Democrats' claims of impeachment.

Rep. Jim Jordan of Ohio, the top Republican on the House Oversight Committee, told reporters after leaving the interview that "not one thing" Volker said "aligns with the Democratic impeachment narrative."

"I do not believe that Volker's testimony advanced Schiff's impeachment agenda," Rep. Mike Turner, an Ohio Republican and House Intelligence Committee member, said in a statement after attending Wednesday's interview. "It is deeply unfortunate and regrettable that Schiff's show trial investigation has clearly affected Volker's ability to advance U.S. interests with Ukraine."

A rough transcript of Turmp's July phone call with Zelensky shows he repeatedly pushed Zelensky to investigate former Vice President Joe Biden, Trump's potential 2020 political rival, and his son, Hunter Biden. There is no evidence of wrongdoing by Joe or Hunter Biden.

The allegations prompted House Speaker Nancy Pelosi to declare Trump had betrayed his oath of office and announce that she was opening a formal impeachment inquiry into the President even before the whistleblower complaint was made available to lawmakers.

The complaint labels Giuliani as a "central figure" in the controversy.

US officials were concerned, the whistleblower said, with Giuliani and his contacts with Ukrainian officials. The whistleblower alleges that US officials believed Giuliani was a conduit for messages between the President and officials in Kyiv and that he was at the helm of a problematic "circumvention of national security decision making processes."

Speaking to CNN last week, Giuliani said he has "no knowledge of any of that crap" in the complaint.

Ahead of his deposition Thursday, dozens of pages of documents were delivered to the House Intelligence, Oversight and Reform and Foreign Affairs committees on behalf of Volker, two sources familiar tell CNN.

Analysts previously told CNN that Volker's testimony could be damaging to the President and his allies.

Volker is seen as "a well-respected straight shooter who is likely to testify in ways that will damage other Trump allies," wrote Ian Bremmer, president of the Eurasia Group, in an emailed analysis. "It's possible others, including key administration members like Secretary of State Mike Pompeo and Attorney General William Barr would also be forced out."

This story has been updated with additional developments Thursday.