Voters headed to the polls in South Carolina on Saturday for the fourth contest in the Democratic presidential nomination race, with Joe Biden looking to salvage his flagging White House hopes

Donald Trump survived the two-year Russia election meddling probe intact, but the revelation that he asked Ukraine to dig up dirt on potential 2020 election campaign rival Joe Biden has now exploded into a scandal threatening his presidency.

Democrats had "no choice" but to launch an impeachment probe into Donald Trump, House speaker Nancy Pelosi said Friday, saying the US president put national security in jeopardy with his attempts to get Ukraine to investigate political rival Joe Biden.

US President Donald Trump on Friday vigorously rejected a whistleblower's claim of wrongdoing, amid reports he used a call with Ukraine's president to pressure him to investigate the son of Trump's Democratic rival Joe Biden.