WASHINGTON (AP) — There was no hinting around, it was a straight-out trade, two key White House officials told impeachment investigators. If Ukraine's new leader wanted an Oval Office welcome from Donald Trump — and he did — he would have to open a public probe into the president's Democratic foe Joe Biden and his son.

"There was no ambiguity," said Lt. Col. Alexander Vindman, an Army officer assigned to the National Security Council, recounting an extraordinary day of meetings at the White House last summer.

According to transcripts released Friday in the House Democrats' impeachment inquiry,...