US President Donald Trump has told reporters on the White House lawn that it is "a scary time for young men" who could become the subject of false accusations.

Key points: Mr Trump said it is scary that accused men are seen as 'automatically guilty'

Mr Trump said it is scary that accused men are seen as 'automatically guilty' Mr Trump said it 'would not be acceptable' if Mr Kavanaugh had lied under oath

Mr Trump said it 'would not be acceptable' if Mr Kavanaugh had lied under oath FBI has finished interviewing Mark Judge, who Dr Ford said witnessed the assault

Asked about allegations of sexual assault in the 1980s levelled against his Supreme Court nominee Brett Kavanaugh, Mr Trump said it was troubling that people were found "automatically guilty" and had to prove their innocence.

"It's a very scary time for young men in America, when you can be guilty of something that you may not be guilty of. This is a very, very, very difficult time," he said.

"You could be somebody that was perfect your entire life, and somebody could accuse you of something — doesn't necessarily has to be a woman … But somebody could accuse you of something, and you're automatically guilty."

However Mr Trump said in response to a reporter's question that it "would not be acceptable" if Mr Kavanaugh had lied to Congress during his testimony.

He followed up the comments with a speech at a rally in Mississippi where he mocked Mr Kavanaugh's accuser, Christine Blasey Ford, for not having answers to some questions during her testimony.

"What neighbourhood was it in? I don't know. Where's the house? I don't know. Upstairs, downstairs, where was it? I don't know. But I had one beer. That's the only thing I remember," Mr Trump said in imitation of Ms Ford's testimony.

"And a man's life is in tatters," he added.

Sorry, this video has expired Mr Trump mocks Dr Ford for not remembering specific details about her alleged assault. ( ABC News )

Democratic Party politicians are raising questions both about the truthfulness of Mr Kavanaugh's sworn testimony to the Senate, and whether he has the temperament for the lifetime appointment to the Supreme Court.

Mr Trump's comments came as Senate Majority Leader Mitch McConnell accused Democrats of opening "the flood gates of mud and muck" against Mr Kavanaugh.

Senators are waiting for the FBI's reopened background check on the accusations against Mr Kavanaugh, who has denied the claims by all three women.

Dr Ford said Mr Kavanaugh assaulted her at high school party. ( ABC News: AP/Andrew Harnik )

The FBI has finished interviewing Mr Kavanaugh's friend Mark Judge, who was said to have attended a high school gathering in the early 1980s where Dr Ford says she was sexually assaulted by the Supreme Court nominee.

A lawyer for Mr Judge, who has denied any wrongdoing, declined to say when the interview finished or what he was asked.

Chuck Schumer, the Senate Democratic leader from New York, said the Senate should be briefed by the FBI at least 24 hours before an initial procedural vote on Mr Kavanaugh's nomination.

He said it's important that senators had a chance to ask directly about what the FBI investigated, what evidence they collected and who they interviewed.

Senator McConnell said a vote would happen on Mr Kavanaugh's nomination by the end of the week.

AP/Reuters