Washington (CNN) US administration officials knew as early as May 2019 that Ukrainian President Volodymyr Zelensky felt pressure from President Donald Trump's allies to conduct investigations that were politically useful to the American president.

That's according to former Trump White House official Fiona Hill, who in recent testimony before Congress said she was told of that pressure contemporaneously by an American businessman and former Obama administration official who had met Zelensky's team on May 7.

This account undercuts the argument from the President and his allies that the Ukrainians did not feel pressure to conduct investigations into Trump's political opponents, including 2020 presidential candidate and former Vice President Joe Biden.

There is no evidence of wrongdoing by Biden in Ukraine.

Hill, who until last month was a top deputy at the National Security Council inside the White House, testified that she heard from one of the participants in that May 7 meeting, former State Department official Amos Hochstein.

According to Hill, Hochstein told her on May 22 that the Ukrainians were concerned about the pressure that then President-elect Zelensky was already facing from Trump's personal attorney, Rudy Giuliani, and his associates, Lev Parnas and Igor Fruman.

She also testified that in mid-May she mentioned these concerns to her boss, then-national security adviser John Bolton, as well as to Bill Taylor, the former Ukraine ambassador who in June became the top US diplomat in Ukraine as head of mission in Kiev.

Hill testified that by mid-May she had also heard similar concerns about Giuliani's pressure campaign from US ambassador to Ukraine Marie Yovanovitch and Phil Reeker, the acting assistant secretary of state for European and Eurasian Affairs.

Hill's account illustrates that US officials were aware Ukrainians felt they were being leaned on to investigate Trump's political rivals long before the July 25 phone call between the two countries' presidents.

Under pressure

On May 7, two weeks before his inauguration, Zelensky and his team held a meeting ostensibly about energy issues. But according to a person familiar with the meeting, the conversation became focused on pressure being put on Zelensky to investigate "corruption," specifically into the Ukrainian energy company Burisma Holdings, on whose board sat Hunter Biden, the son of Joe Biden.

Trump and his allies have leaned heavily on a Sept. 25 statement from Zelensky that he did not feel pressured to investigate.

But the May 7 meeting suggests that's not the case. The person familiar with the meeting told CNN that even in those early weeks after his election, Zelensky and his team realized Ukraine's relationship with the US -- including a potential face-to-face meeting with Trump -- could be at stake if they did not support the continuation of investigations like Burisma.

According to Hill's testimony, that was alarming enough to prompt Hochstein, who sits on the supervisory board of Naftogaz, the state-owned Ukrainian energy corporation, to request to meet with her.

"He also said that a number of Ukrainian officials had come to him very concerned that they were getting pressure from Giuliani and Giuliani associates," Hill said.

That meeting happened about two weeks after Zelensky and Trump spoke for the first time following Zelensky's electoral victory in late April. A White House readout of that call released at the time said the two leaders discussed working together to "root out corruption."

But there is no such mention of corruption, either generally or specifically about Burisma, in the transcript of that April call, which the White House released last week . There is no evidence of wrongdoing by either Biden in Ukraine.

Pressure on Naftogaz

In addition to the pressure about pursuing investigations into Burisma, Hill testified that Hochstein told her of a push from two of Giuliani's associates, Parnas and Fruman, to change the composition of Naftogaz's board.

Parnas and Fruman, who were charged in federal court last month for campaign-finance violations and money laundering, assisted Giuliani in gathering information for his push for Ukraine to investigate Burisma.

According to an American businessman named Dale Perry, who was familiar with their efforts, Parnas and Fruman were also involved in an effort to reorganize Naftogaz , pushing a scheme at a major energy conference in Houston in March to replace the company's chief executive officer with someone who would be more beneficial to their own business interests.

And around the time of Zelensky's inauguration in May, US Energy Secretary Rick Perry (no relation to Dale Perry) provided a list of names to Ukrainian officials of potential replacements for Hochstein on the Naftogaz supervisory board.

Perry's goal, according to a former US official involved in Ukraine, was to replace Hochstein with someone more known and favorable in Republican circles.

At a press conference in Lithuania in October, Perry disputed he was advocating for specific people to be placed on the board.

"That was a totally dreamed up story the best I can tell," he said. "We gave recommendations at the request of the Ukrainian government and will continue to."