In a secret interview, Rep. Adam Schiff, leader of the House Democratic effort to impeach President Trump, pressed former United States special representative to Ukraine Kurt Volker to testify that Ukrainian officials felt pressured to investigate former Vice President Joe Biden's son Hunter as a result of Trump withholding U.S. military aid to Ukraine.

Volker denied that was the case, noting that Ukrainian leaders did not even know the aid was being withheld and that they believed their relationship with the U.S. was moving along satisfactorily, without them having done anything Trump mentioned in his notorious July 25 phone conversation with Ukrainian President Volodymyr Zelensky.

When Volker repeatedly declined to agree to Schiff's characterization of events, Schiff said, "Ambassador, you're making this much more complicated than it has to be."

The interview took place Oct. 3 in a secure room in the U.S. Capitol. While the session covered several topics, the issue of an alleged quid pro quo — U.S. military aid in exchange for a Ukrainian investigation of the Bidens and a public announcement that such an investigation was underway — was a significant part of the discussion.

"[The Ukrainians] didn't want to be drawn into investigating a Democratic candidate for president, which would mean only peril for Ukraine, is that fair to say?" Schiff asked Volker.

"That may be true," Volker said. "That may be true. They didn't express that to me, and, of course, I didn't know that was the context at the time." (Volker has said he did not know that Trump had mentioned the Bidens on the July 25 call with Zelensky until the rough transcript of the call was released on Sept. 25.)

"Part of the other context is vital military support is being withheld from the Ukraine during this period, right?" Schiff asked.

"That was not part of the context at the time," Volker said. "At least to my knowledge, they [Ukrainian leaders] were not aware of that."

Schiff asked whether Volker had discussed the withholding of aid with Ukrainian officials. Volker said he had not. The first time he talked with the Ukrainians about that was when a story appeared in the press, an article in Politico, "Trump holds up Ukraine military aid meant to confront Russia," on Aug. 28-29, well after the July 25 Trump-Zelensky phone call.

"The first conversation I had was when the diplomatic adviser to President Zelensky, Vadym Prystaiko, I believe it was, texted me a copy of the Politico article about the hold on assistance," Volker testified. "So I had had many conversations with him in the months prior to that, and this did not come up from him to me, which makes me believe that this was not on his radar until that time when he saw the article."

Volker said that he already knew about the suspension in aid, having learned on July 18, a week before the Trump-Zelensky call. Volker testified that he asked around about the suspension — why was it being done? — but was not able to find out what was going on.

Schiff began to push the quid pro quo allegation. He asked Volker whether he would agree that "no president of the United States should ever ask a foreign leader to help intervene in a U.S. election."

"I agree with that," said Volker.

"And that would be particularly egregious if it was done in the context of withholding foreign assistance?" Schiff continued.

Volker balked. "We're getting now into, you know, a conflation of these things that I didn't think was actually there."

Schiff wanted Volker to agree that "if it's inappropriate for a president to seek foreign help in a U.S. election, it would be doubly so if a president was doing that at a time when the United States was withholding military support from the country."

Again, Volker did not agree. "I can't really speak to that," he said. "My understanding of the security assistance issue is — "

Schiff interrupted. "Why can't you speak to that, ambassador? You're a career diplomat. You can understand the enormous leverage that a president would have while withholding military support from an ally at war with Russia. You can understand just how significant that would be, correct?"

Volker tried to go along without actually agreeing. "I can understand that that would be significant," he said.

Schiff persisted. "And when that suspension of aid became known to that country, to Ukraine, it would be all the more weighty to consider what the president had asked of them, wouldn't it?"

"So again, congressman, I don't believe — " Volker began.

"It's a pretty straightforward question," Schiff said.

"But I don't believe the Ukrainians were aware that the assistance was being held up — "

"They became aware of it," Schiff said.

"They became aware later, but I don't believe they were aware at the time, so there was no leverage implied," Volker said.

The two men continued to argue about the chronology of events. By the time the Ukrainians learned about the withheld aid in late August, Volker said, all sides had dropped the idea of making a statement announcing an investigation of the Bidens and events during the 2016 election. But Schiff kept pushing the notion that once the Ukrainians did learn about the withheld aid, then they would have felt tremendous pressure from Trump.

"At the point they [the Ukrainians] learned that, wouldn't that have given them added urgency to meet the president's request on the Bidens?" Schiff asked.

"I don't know the answer to that," Volker said.

Schiff pressed Volker to agree one more time. In response, Volker tried to explain that the Ukrainians did not seem to be feeling pressure from Trump and the U.S.

"Congressman, this is why I'm trying to say the context is different, because at the time they learned that, if we assume it's Aug. 29, they had just had a visit from the national security adviser, John Bolton. That's a high-level meeting already. He was recommending and working on scheduling the visit of President Zelensky to Washington. We were also working on a bilateral meeting to take place in Warsaw on the margins of a commemoration on the beginning of World War II. And in that context, I think the Ukrainians felt like things are going the right direction, and they had not done anything on — they had not done anything on an investigation, they had not done anything on a statement, and things were ramping up in terms of their engagement with the administration. So I think they were actually feeling pretty good then."

At that point, Schiff gave up. Why was Volker resisting? "Ambassador, I find it remarkable as a career diplomat that you have difficulty acknowledging that when Ukraine learned that their aid had been suspended for unknown reasons, that this wouldn't add additional urgency to a request by the president of the United States. I find that remarkable."

Later, Republican Rep. Scott Perry questioned Volker, returning to the colloquy with Schiff. Perry asked Volker whether he, Volker, had close relations with Ukrainian officials and whether, if those officials felt something was amiss, they would tell Volker.

"The folks that you dealt with in Ukraine at the very highest level, I don't know, but I'm going to ask, do you feel like they had a fair amount of trust in you?"

"Absolutely," said Volker.

"So they would confide things in you if they had a question?"

"They would confide things," Volker answered. "They would ask questions. They would ask for help. We had a very candid relationship ... "

"In your conversation with Rep. Schiff, he kind of implied and wanted you to intimate that there was an agreement based on that conversation that: If you do the investigation, then you can have a meeting [with Trump] and maybe we'll consider this military aid. If that were the case from the call, do you feel, because they had some trust in you, that they would have come to you and said, 'Hey how do we handle this? Is this what the President of the United States is asking?' Would they confide — would they ask you that?"

"Yes," said Volker. "They would have asked me exactly that, you know. How do we handle this?"

Much of the coverage of Volker's testimony focused on his opening statement, which made its way to the media. (Washington Post headline: "Volker defends Biden as 'man of integrity' in testimony to Congress.") But there was much more to the testimony than the opening statement. Among other things, it showed how Schiff, as a powerful chairman in charge of impeachment, pursues his theory of the case even when a witness gives testimony that does not support it.

Schiff has scheduled more interviews for this week and next.