US Democrats launch impeachment proceedings against Trump

The US Democratic Party took a huge gamble on Tuesday and started impeachment proceedings against President Donald Trump over allegations he pressured Ukraine to investigate his political rival Joe Biden.

US House of Representatives speaker Nancy Pelosi said the probe would look at whether Trump tried to leverage the Ukrainians by withholding military in return for an investigation into unsubstantiated corruption allegations against Biden and his son Hunter.

Biden is currently the leading Democratic Party candidate to challenge Trump in the 2020 presidential election.

"The president must be held accountable. No one is above the law," Pelosi told a news conference on Tuesday. "This week the president has admitted to asking the president of Ukraine to take action that would benefit him politically."

A furious Trump called the move "witch hunt garbage".

Democrats control the House of Representatives and there is widespread support among their members for impeachment, but it is unlikely that the investigation will get through Republican-controlled Senate where a two-thirds majority is required to unseat Trump.