Two top national security aides who listened to President Donald Trump's July call with Ukraine's president, are testifying at US House impeachment hearings as the inquiry probes deeper into goings-on the White House.
Lieutenant Colonel Alexander Vindman, an Army officer at the National Security Council, and Jennifer Williams, his counterpart at Vice President Mike Pence's office, say they had concerns as Trump spoke on July 25th with the newly elected Ukraine president about political investigations into Joe Biden.
In total, nine current and former US officials are testifying as the House's impeachment inquiry accelerates.