(CNN) US Ambassador Gordon Sondland said in an interview a day after President Donald Trump's July phone call with Ukraine's leader that the United States would increase its support of the country if it undertook "promised" reforms.

Sondland, the US ambassador to the European Union, did not specify in the July 26 interview with Radio Liberty what those reforms were, only saying there was a "long list of reforms" and that Ukraine's President Volodymyr Zelensky would need to show "political will" to undertake them.

Sondland is set to testify publicly before the House Intelligence Committee on Wednesday, where he is at the center of allegations that the Trump administration withheld military aid to Ukraine as a way to pressure the government into announcing investigations into Trump's political rivals, namely former Vice President Joe Biden, and a debunked conspiracy theory that Ukraine was behind the hack of the Democratic National Committee in 2016.

The July interview, which has not been widely reported on, was surfaced by CNN's KFile as part of a review of Sondland's public comments about Ukraine. Sondland's comments in the interview shed new light on his mindset around the time of Trump's July 25 phone call with Zelensky. Sondland spoke with Trump before and after that call, according to congressional testimony and an interview with Ukrainian television.

Sondland's interview shows that "promised" reforms were front and center -- though it's unclear whether Sondland was referring to Zelensky's promises to the Ukrainian people or his willingness to give in to Trump's demands. Zelensky campaigned on promises to reform Ukraine and rein in corruption, which has plagued the country for years. Sondland's public comments in the interview were the same exact day he privately told Trump that Zelensky "loves your ass" and is "gonna do" the investigation into Biden, according to congressional testimony.