Two top US diplomats delivered gripping testimony about Donald Trump's efforts to get Ukraine to investigate Bidens.
Democrats accuse Trump of abusing his power by using US military assistance and a possible White House meeting to pressure President Volodymyr Zelensky into opening a probe into the Democrat Biden and his son Hunter, who served on the board of Ukrainian gas company Burisma.
Asked about the new allegations, while hosting his Turkish counterpart Recep Tayyip Erdogan at the White House, Trump replied: "First time I've heard it."