Video report by ITV News Washington Correspondent Robert Moore
Former US President Barack Obama has lamented that his country faces a tough battle to end division and undo what he called "truth decay".
Speaking to CBS News, President Obama - US presidents maintain their title after leaving office - said the silence of US Republicans was a perilous sign for democracy in the US.
"The President doesn't like to lose and never admits loss," he told CBS News, but added: "I'm more troubled by the fact that other Republicans - who clearly know better - are going along with this."
In an interview with Oprah Winfrey ahead of the release of his new memoir, the 59-year-old said he was "personally invested in" President-elect Biden and Vice President-elect Harris.
Joe Biden was Barack Obama's Vice-President during the latter's time in the White House.
Though the Biden-Harris win is yet to be acknowledged by President Trump, his predecessor said their success gives America the chance "to get back to the kind of competent, caring government that we so badly need".
While looking ahead to the next Democrat in the White House, Mr Obama reflected on his own time at the top and revealed the worst day of his own presidency.
Quizzed on gun violence in the US, President Obama described the Sandy Hook Elementary School shooting in 2012 as the "saddest" day of his presidency.
The mass shooting in Connecticut claimed the lives of 26 people - including 20 children who were six and seven-years-old.
President Obama described Sandy Hook as "the saddest day" of his presidency.
He added the lack of action across the US political system in the aftermath of the shooting left him "the angriest" he had been during his eight year term.
"When Congress failed to do anything in the aftermath of Sandy Hook, was probably the angriest I ever was during my presidency," he said.
"I was disgusted and appalled during the inaction".
President Obama said gun violence has "become such a cultural hot button issue" and, at the time, was viewed as "politics" rather than a human issue.