Mr Obama appeared before the press corps alongside visiting Italian Prime Minister Matteo Renzi, where he took the opportunity to field questions about the Republican nominee.

“I invite Mr Trump to stop whining and try to make his case to get votes,” Mr Obama said. He added that Mr Trump’s claims are “not based on facts”.

“He’s already whining before the game’s even over,” he said, explaining the likelihood of Mr Trump contesting the results of the election is “one way of weakening America and making it less great”.

On Putin, Mr Obama called Mr Trump’s “continued flattery” of the Russian president “unprecedented” in US politics.

The praise, Mr Obama added, is “out of step with not just what Democrats think, but out of step with what – up until the last few months – almost every Republican thought, including some of the ones who are now endorsing Mr Trump”.

Donald Trump calls sexual abuse allegations 'pure fiction'

Mr Trump has expressed praise for Mr Putin, suggesting that he is a stronger leader than the current US president for months throughout his campaign. Nonetheless, Republican supporters did not defect until the emergence of a 2005 video that captured Mr Trump bragging about sexual assault during an Access Hollywood taping.

Republican leaders backing away from Donald Trump after lewd remarks Show all 12 1 /12 Republican leaders backing away from Donald Trump after lewd remarks Republican leaders backing away from Donald Trump after lewd remarks Former governor of California Arnold Schwarzenegger Schwarzenegger said he will not vote for Trump Getty Republican leaders backing away from Donald Trump after lewd remarks Senate Majority Leader Mitch McConnell Mr McConnell condemned the remarks, but has not unendorsed him Getty Republican leaders backing away from Donald Trump after lewd remarks House Speaker Paul Ryan Mr Ryan disinvited Mr Trump from a Wisconsin campaign event following the remarks Getty Republican leaders backing away from Donald Trump after lewd remarks Former Sec of State Condoleezza Rice Ms Rice called for Trump to withdraw his candidacy Getty Republican leaders backing away from Donald Trump after lewd remarks Nebraska Sen Deb Fischer Ms Fischer called on Trump to step aside and give nomination to Mike Pence Getty Republican leaders backing away from Donald Trump after lewd remarks Texas Sen Ted Cruz Mr Cruz denounced the remarks, but still endorses Trump Getty Republican leaders backing away from Donald Trump after lewd remarks Former Republican candidate Carly Fiorina Ms Fiorina wants Mike Pence to take the nomination Getty Republican leaders backing away from Donald Trump after lewd remarks Conservative radio host Hugh Hewitt Hewitt called for Trump to step down Getty Republican leaders backing away from Donald Trump after lewd remarks Utah Representative Mia Love Ms Love said she cannot vote for Trump after hearing his remarks Getty Republican leaders backing away from Donald Trump after lewd remarks Former New York Gov George Pataki Mr Pataki said Mr Trump should step down Getty Republican leaders backing away from Donald Trump after lewd remarks New Hampshire Sen Kelly Ayotte Ms Ayotte will write in Mike Pence when she votes Getty Republican leaders backing away from Donald Trump after lewd remarks Arizona Sen John McCain Mr McCain will choose Mike Pence on Election Day Getty

As more and more accusers surfaced in various media reports, Mr Trump began to deflect scrutiny and criticism for the sexual assault allegations – coupled with his previous braggadocio about such acts – with shouts of collusion between the political press and the Clinton campaign.

“The election is being rigged by corrupt media pushing false allegations and outright lies in an effort to elect Hillary Clinton president,” Mr Trump said at a campaign stop Maine on Saturday. "We are going to stop it. We are not going to back down.”