Washington, August 4 (RHC)-- With less than 100 days left before the November election, U.S. President Barack Obama offered his strongest criticism of Republican presidential nominee Donald Trump so far, urging Republican leaders to withdraw their endorsements of his candidacy.

Obama said that the Republican candidate for the November elections is not fit to occupy the White House and should not be elected to the office. He said that Trump was “woefully unprepared” to serve as president, and asked why Republicans kept distancing themselves from the candidate while still supporting him.

Meanwhile, friction is increasing between Trump and top Republican leaders. In an interview with The Washington Post, Trump refused to endorse the re-election campaigns of Arizona Senator John McCain and Wisconsin Congressmember Paul Ryan.

Instead, Donald Trump praised Ryan’s opponent in the race, saying he was "running a very good campaign." Ryan’s opponent, Paul Nehlen, has defended Trump and says he's got his vote.

Both Paul Ryan and John McCain have publicly distanced themselves from Donald Trump, whom they reluctantly endorsed when the Republican nominee won the party's top candidacy for the upcoming elections.