At issue is Trump's decision to tie military aid for Ukraine to investigations of Joe Biden and the Democrats. Allies of the president say he did nothing wrong because the Ukrainians never knew the aid was being delayed.
The special adviser for Ukraine at the State Department, Catherine Croft, says she fielded inquiries from Ukraine about the holdup.
In the transcript of her testimony to House investigators, released Monday, Croft says officials in Ukraine were clear in their concern over the assistance as they battled Russian aggression.
Witnesses in the impeachment inquiry are set to begin testifying in public on Wednesday.