EU ambassador to testify he believed meeting with Trump conditioned on investigation announcement

The U.S. ambassador to the European Union is expected to testify Thursday that he believed that a Ukrainian government statement announcing investigations requested by President Donald Trump was a condition for a meeting between Trump and Ukrainian President Volodymyr Zelenskiy, sources familiar with his planned testimony before congressional investigators tell ABC News.

It would be a remarkable accusation from Gordon Sondland, the Trump mega donor-turned-diplomat who has emerged as a central character in the rapidly unfolding impeachment inquiry -- essentially confirming what critics have charged, that Trump wanted a so-called "quid pro quo" exchange for investigations that might benefit him politically.

It also runs counter to what Sondland told a senior U.S. diplomat in text messages obtained by the three House committees investigating impeachment from Kurt Volker, the former special envoy for Ukraine. In those exchanges, Sondland said Trump had "been crystal clear no quid pro quo's of any kind."

A lawyer for Sondland didn’t immediately respond to ABC’s request for comment.

Republican lawmakers -- and Trump himself -- have pointed to this text as evidence that Trump did not participate in any wrongdoing. But sources familiar with Sondland's testimony told ABC News that he's expected to tell congressional investigators that he had spoken to the president before sending that text message and he was just relaying what the president told him, not because he had any direct knowledge on the matter.

Volker and Sondland were working with Zelenskiy and his top aides to secure a White House meeting between Trump and the new president -- eager for U.S. support. In the texts, first obtained by ABC News, they make clear to a top Zelenskiy aide that in a July 25 phone call, Zelenskiy must convince Trump that "he will investigate / 'get to the bottom of what happened in 2016'" in order for them to "nail down date for visit to Washington," as Volker writes.

During that call, Trump asked Zelenskiy to "do us a favor" and work with his personal lawyer Rudy Giuliani and Attorney General William Barr to open investigations, and then invited him to reach out to set up a visit to the White House.

"Whenever you would like to come to the White House, feel free to call," Trump said on the call, according to a rough transcript released by the White House. "Give us a date and we'll work that out. I look forward to seeing you.”

The text messages raised eyebrows from Democrats who said the messages could be used as additional evidence that Trump had conditioned U.S. security assistance and meetings with Ukraine's leader on the opening of a politically beneficial investigation into Democratic presidential candidate Joe Biden and his son Hunter's relationship with the Ukrainian energy company Burisma Holdings.

To date, Zelenskiy still has not visited Trump at the White House, but the two leaders did meet in late September at the United Nations General Assembly meeting in New York.