"This witness is potentially very important and of course we are moving to depose this witness and we have already scheduled their deposition", Schiff said on Wednesday. "In terms of the new information that Ambassador Taylor gave about this conversation … one of Ambassador Taylor’s staff is overhearing a conversation between Sondland and the president", he added. "The president is interested in whether the Ukrainians are going to do the investigation and Sondland assures him that they are".
The testimony is important, Schiff said, because it will show the president giving top-down instructions to subordinates, whom Schiff fears Trump allies will attempt to discredit as he impeachment probe continues.
Earlier on Wednesday, Taylor told the impeachment panel: "Following the call with President Trump, the member of my staff asked Ambassador Sondland what President Trump thought about Ukraine. Ambassador Sondland responded that President Trump cares more about the investigations of Biden".
Later on Wednesday, Trump denied any knowledge of the purported conversation.
Biden has publicly admitted that as vice president, he threatened to withhold $1 billion in US military aid to Ukraine unless the country fired a prosecutor who was investigating corruption at Bursima, a company that employed his son, Hunter.
Democrats, who control the impeachment probe, have refused Republican requests to have Hunter Biden testify about his work for Bursima when his father was vice president.
In a 26 July conversation, Trump reportedly pressed Sondland on whether Ukraine would open an investigation of former Vice President Joe Biden and his son Hunter as requested by Trump a day earlier.
The conversation took place the day after a White House meeting in which Trump asked Ukraine President Volodymyr Zelensky to investigate Biden.