WASHINGTON (Reuters) - The top U.S. diplomat in Ukraine, William Taylor, told lawmakers he believed the push to investigate Ukrainian energy company Burisma and its ties to Hunter Biden was motivated by a desire to attack Hunter’s father, former Vice President Joe Biden.

“As I understood the reason for investigating Burisma was to cast Vice President Biden in a bad light,” Taylor said, according to a transcript of closed-door testimony he delivered as part of an impeachment investigation into President Donald Trump. The committees leading the probe released the transcript on Wednesday.

Biden is a leading candidate for the Democratic presidential nomination, making him one of President Donald Trump’s main political rivals.