After the speaker of the lower house, Nancy Pelosi, upped the ante by suggesting that Mr Trump come forward to tell the "truth", the Republican president said he was keen.
On Monday evening, House committees released the transcript of a State Department official who testified in the impeachment inquiry November 15 that he overheard the president tell the USA envoy to the European Union that he was seeking political investigations from Ukraine's president.
House Democrats were sceptical. "He should allow top White House aides to testify". He should end his illegal coverup. The special counsel's office requested an in-person interview with Trump multiple times, which he declined.
Thirty-two percent of Americans said they had already decided that Trump should be impeached "before the Ukraine scandal erupted into public consciousness".
Among the eight to testify publicly this week is the current USA ambassador to EU, Gordon Sondland, who was among the key Trump aides at the heart of the effort to force Ukraine to launch an investigation against former Vice-President Joe Biden and his son Hunter Biden over latter's association to a Ukrainian energy company, as a condition for releasing almost $400 million in security aid and according a White House meeting to President Volodymyr Zelensky. "President Trump is welcome to take a seat right there". He relayed details from an explosive July 10 meeting at the White House, saying the ambassador pushed visiting Ukraine officials for the investigations Trump wanted. The money, approved by the U.S. Congress to help U.S. ally Ukraine combat Russia-backed separatists, was later provided.
The invitation comes as the House intelligence committee is set to hear more testimonies in the second week of the inquiry's public hearings.
In the latest development, state department official David Holmes told investigators in closed door testimony on Saturday that he had overheard a U.S. diplomat telling Mr Trump that Ukraine would carry out investigations the president had asked for.
House general counsel Douglas Letter made the statement to the court to explain why the congressmen need access quickly to secret grand jury material Mueller gathered during his probe. He will likely be asked about a July 26 gathering at a Kiev restaurant where Sondland called Trump on his cellphone from a table on the outdoor terrace.
Multiple witnesses overheard a phone call in which Trump and Sondland reportedly discussed efforts to push for the investigations.
"So he's gonna do the investigation?"
The accounting firm has said that it will turn over the documents the prosecutors want if Trump loses the case.
Trump has said he has no recollection of the overheard call and has suggested he barely knew Sondland, a wealthy donor to his 2016 campaign.
Several witnesses testified last week that they were alarmed over the pressure tactics used against Ukraine, as well as the role of Trump's personal lawyer, Rudy Giuliani.