Joe Biden, the frontrunner for the Democratic presidential nomination, has vowed to defeat Republican President Donald Trump in next year's election.
Biden said on Wednesday: "Let me clarify something to Trump and his men hired and special interests who finance his attacks against me .. I will not withdraw .. You will not destroy me, will not destroy my family."
Biden accused President Trump of abuse of power. He said the US president's accusations against him and his son Hunter were "fired because he is as scared as any authoritarian and bullying in history ... He is afraid of the harsh defeat that I will inflict on him in November."
The mutual attack came after Trump strongly denounced via a series of tweets, and then at a press conference, an investigation into his isolation related to a telephone call he made in June with his Ukrainian counterpart in which he asked to investigate Biden and his son Hunter, who served on the board of a Ukrainian company when his father was a deputy. For President Obama.
Democrats accused Trump of putting pressure on a US ally (Ukraine) to intervene in the 2020 presidential election for his own political advantage.