Acting assistant secretary of state Philip Reeker was expected to testify in the impeachment inquiry today that he did not find out there was a push by Trump administration officials for Ukraine to publicly announce investigations into Vice President Joe Biden and the 2016 election until the whistleblower complaint was made public, a source familiar with his testimony told CNN.

While Reeker's testimony for the Democratic led House impeachment inquiry appeared to be absent the more explosive allegations that came from depositions earlier in the week with regard to the assistance, his comments are expected to color in details surrounding the firing of the Marie Yovanovitch, the former US ambassador to Ukraine who was discharged at President Trump's behest.

Reeker is testifying behind closed doors in a rare Saturday session before the House Intelligence, Foreign Affairs and Oversight committees as part of the impeachment inquiry sparked by a whistleblower complaint alleging Trump pushed Ukraine to open investigations that would help his reelection campaign at the same time that US security aid to Ukraine had been frozen.

Some background on Reeker: He was involved in the discussions about Yovanovitch dating back to his first week on the job in March.

Reeker was an advocate of an internal push for the State Department to put out a statement of support for Yovanovitch when she left the post. But other top State Department officials under Secretary Mike Pompeo forbid the kind of statement he thought was necessary.

Reeker has known Yovanovitch for over 20 years and, as many other foreign service officers, supported her work.

Yovanovitch said that she was told the decision was due to Trump losing confidence in her based on "unfounded and false claims by people with clearly questionable motives."