biden investigation and ambassador sondland believed and related to me that the president was giving him instruction. sondland has already had to amend his testimony. and no one knows how truthful he's going to be when he testifies. especially given the fact that as alex marquardt reports, president trump has been attacking multiple other witnesses. >> reporter: this week poised to be the most blockbuster few days so far in the impeachment inquiry after revelations over the weekend place gordon sondland, the ambassador, at the center of the ukraine scandal because of his direct access to president trump. >> we'll have to wait for sondland's testimony which is direct testimony, not testimony of somebody who said they heard from somebody else that somebody else said something. >> reporter: sondland is set to testify in an open hearing on wednesday. tim morrison testified that sondland was following the president's orders in demanding ukraine launch investigations