President Trump has confirmed that he raised the subject of former Vice-President Joe Biden and his son in a July phone call with Ukrainian president Volodymr Zelensky.
Mr Trump is facing allegations that he pressured Ukraine to investigate his potential 2020 rival, which he denies.
But his admission about the phone call fuelled calls for Democrats to launch impeachment proceedings in Congress.
Adam Schiff, a senior Democrat, said Mr Trump may have “crossed the Rubicon”. Read more