Washington (CNN) The US Ambassador to the European Union kept several Trump administration officials briefed on his attempts to get Ukraine to launch investigations later discussed in Trump's July call with Ukrainian President Volodymyr Zelensky, emails reviewed by The Wall Street Journal show.

Gordon Sondland, U.S. ambassador to the European Union, arrives to the Capitol for his deposition as part of the House's impeachment inquiry on Thursday, October 17.

The emails reviewed by the Journal show Gordon Sondland -- who testified last month he was directed by Trump to work with Rudy Giuliani on Ukraine -- kept acting White House chief of staff Mick Mulvaney and Energy Secretary Rick Perry informed of his push for the country to launch investigations in the weeks leading up to Trump's July 25 call with his Ukrainian counterpart.

A rough transcript of the call released by the White House shows Trump 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 either Biden.

News of Sondland keeping top Trump officials apprised of his efforts with Ukraine comes just days before he is set to testify publicly in the House impeachment investigation. State Department aide David Holmes testified last week he overheard a phone conversation where Sondland told Trump that Zelensky "loves your ass" and that Ukraine was going to move forward with the investigation Trump had asked Zelensky for a day earlier.

Holmes explained that Sondland had placed the call to Trump, and he could hear Trump because the call was so loud on the terrace of a restaurant, where they dined with two others.

"While Ambassador Sondland's phone was not on speakerphone, I could hear the President's voice through the earpiece of the phone. The President's voice was very loud and recognizable, and Ambassador Sondland held the phone away from his ear for a period of time, presumably because of the loud volume," Holmes testified.

Sondland's text messages with the top US diplomat in Ukraine, Bill Taylor, are a key data point for the impeachment investigation, in which Sondland told Taylor there was "no quid pro quo" after speaking to Trump about the matter.

Sondland's testimony says that he knew of no arrangement tying US security assistance to Ukraine with an investigation into the Bidens -- but also that it would be wrong to do so.

"Let me state clearly: Inviting a foreign government to undertake investigations for the purpose of influencing an upcoming U.S. election would be wrong," Sondland said, according to the statement. "Withholding foreign aid in order to pressure a foreign government to take such steps would be wrong. I did not and would not ever participate in such undertakings. In my opinion, security aid to Ukraine was in our vital national interest and should not have been delayed for any reason."

The House's fast-moving impeachment inquiry is rooted in a whistleblower complaint alleging that Trump abused his official powers "to solicit interference" from Zelensky in the upcoming 2020 election, and the White House took steps to cover it up.

Even before the whistleblower complaint was made available to lawmakers, House Speaker Nancy Pelosi declared Trump had betrayed his oath of office and announced she was opening a formal impeachment inquiry into the President.