Former President Barack Obama has shied away from endorsing Vice President Kamala Harris in her US presidential bid over doubts about her ability to defeat Republican rival Donald Trump, according to a source close to the Biden family.

Following the surprise resignation of 81-year-old Joe Biden from the US presidential election and his prompt endorsement of Harris, the majority of Democratic leaders quickly embraced Harris's candidacy. But the 44th US President famously declined to support her. "He knows she can't win, which is why he's very upset," the Biden family sources told the New York Post.

"Obama knows she's just incompetent-the border czar who's never visited the border, advocating that all migrants should have health insurance. She's not equipped to navigate the challenges ahead." The pivotal moment for 81-year-old Biden occurred during his critically acclaimed debate performance against Trump in Atlanta last month, which was purportedly planned to eliminate him from the contest.

The source predicted that Harris would make mistakes on matters such as Israel, Palestine, and Ukraine, and voiced doubt about her chances of defeating Trump in a broadcast discussion. She is incapable of debating. The insider declared, "She's going to put her foot in her mouth." According to the source, Obama's initial hope was to clear the path for Biden's exit, a strategy bolstered by an article from George Clooney urging Biden to step aside.