Democrats allege that Trump suspended the aid package to pressure Ukrainian President Volodymyr Zelensky to probe the president's Democratic rival, former Vice President Joe Biden.
"We have another transcript coming out which is very important", Mr Trump told reporters at Joint Base Andrews before leaving for a visit to Tuscaloosa, Alabama.
Hill recalled Sondland saying that acting White House Chief of Staff Mick Mulvaney had agreed Trump would meet with Ukraine's president if they opened investigations into "the energy sector", which she said was code for Burisma.
-Investigators in the inquiry on Friday released hundreds of pages of testimony from Fiona Hill, a former White House Russia adviser, and Lt. Col. Alexander Vindman, an Army officer assigned to the National Security Council.
The subpoena comes following House investigators' request on Tuesday that Mulvaney testify on Capitol Hill at the end of the week, ratcheting up their investigation to target the President's top aide.
United States congressional committees conducting an impeachment probe of President Donald Trump met on Thursday (Nov 7) for the first time with an adviser to Vice-President Mike Pence, but former national security adviser John Bolton failed to heed a request to appear. Vindman explained to the lawmakers he found it concerning because if a more powerful United States asked Ukraine to investigate a private USA citizen, Kiev may think it's in its national security interests to do so and deliver results favorable to Washington. Trump said Saturday he has no problem making details of that call public. "But this is the man who said there was no quid pro quo, and he still said that".
The inquiry was triggered by a complaint filed by a person who remains anonymous, though an alleged name has been reported in several media outlets.
Mulvaney's defiance came after former national security adviser John Bolton also failed to appear for an interview Thursday. It was not immediately clear whether the president was referring to that call or another unreported conversation he held with his Ukrainian counterpart, The Independent said.
Mulvaney will have to appear before the committees Friday, according to the report.
He also testified that he was sidelined from official USA policy on Ukraine when a second channel of decision-making rose in late summer, with the influence of partisan figures such as President Donald Trump's attorney Giuliani overtaking and even blocking the work of officials and government staff. Pence called the impeachment inquiry a "disgrace".