US President Barack Obama has said Republican nominee Donald Trump is unfit to be president, and questioned why his party still supports the New York billionaire's candidacy, reports the BBC.
"There has to come a point at which you say: 'Enough'," Mr Obama said.
Mr Trump is under fire for attacking the parents of a dead US Muslim soldier after they criticized him.
On Tuesday, he turned on two senior figures in his own party who have publicly criticized him.
In an interview for the Washington Post, he refused to endorse House Speaker Paul Ryan and Senator John McCain, who are up for re-election in November.
Mr Trump, who faces the Democrats' Hillary Clinton in November's presidential election, has also been condemned for backing the Russian annexation of Crimea.
Mr Obama said he had had policy differences with previous Republican presidents and candidates-- but added that he had never thought they could not function as president.