A Republican senator has launched an attack on Donald Trump as unfit to lead an America divided by the looming vote on Brett Kavanaugh’s Supreme Court nomination.

Ben Sasse used a Senate speech to lambast the president for publicly mocking Christine Blasey Ford, who has accused Mr Kavanaugh of sexually assaulting her when they were in high school.

And he said the US had become riven by black-and-white “tribalism” over Mr Kavanaugh’s nomination. He insisted the impending vote on whether to confirm the judge’s elevation to the country’s highest court was not ”a giant binary choice about the much broader issue of whether we do or don’t care about women”.

The Nebraska Republican said on Wednesday night: ”We all know that the president cannot lead us through this time. We know that he’s dispositionally unable to restrain his impulse to divide us.

“His mockery of Dr Ford last night in Mississippi last night was wrong, but it doesn’t really surprise anyone – it’s who he is.

Video: WH Defends Trump's Comments About Dr. Ford As 'Facts'

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“Similarly it was wrong last week when he said that, quote, ‘If the attack on Dr Ford was as bad as she says, charges would have been immediately filed with local law enforcement authorities’.

“It’s wrong when people insinuate that a woman bears blame for her sexual assault because she was drunk. This reinforces the stereotypes that have caused millions of women to bury their experiences of abuse and assault for decades.

“This kind of repugnant nonsense creates excuses for abusers.”

At a campaign rally on Tuesday, Mr Trump imitated Dr Ford while mocking her lack of recollection of some details on the night she alleges Mr Kavanaugh attacked her.

It marked a sharp departure from his previous treatment of Dr Ford. While making clear he still backed his nominee, the president had described his accuser as a “very credible witness”.

In his address on Wednesday night, Mr Sasse, a member of the judiciary committee, said he had “urged the president to nominate a woman” to the Supreme Court before Mr Trump announced he was picking Mr Kavanaugh on 9 July, but did not say who in particular he had suggested.

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“Although I’ve said many complimentary things about Judge Brett Kavanaugh and his distinguished record of 12 years of service on the DC circuit court, I will say I urged the president, back in June and early July, to make a different choice before he announced this nomination,” he said.

“I urged him to nominate a different individual, I urged the president to nominate a woman.

“Part of my argument then was that the very important Me Too movement was also very new and that this senate is not at all well prepared to handle potential allegations of sexual harassment and assault that might have come forward. This was absent knowing a particular nominee.”

Observers have cast doubt on whether Mr Sasse will run for re-election to the Senate in 2020 following his claim earlier this year that he considered leaving the Republican Party “every day”.

It came as senators prepared to review the results of an FBI background investigation into Mr Kavanaugh, following a string of sexual assault claims against the nominee.

A copy of the agency’s probe will be made available at a secret Capitol Hill location.

The White House believes the investigation contains no information that corroborates the allegations against Mr Kavanaugh, according to the Wall Street Journal, while Democratic senator Dianne Feinstein criticised the FBI for failing to interview either the nominee or his most prominent accuser, Christine Blasey Ford.

Senators are expected to vote on moving forward with Mr Kavanaugh’s nomination on Friday, with a final confirmation vote likely over the weekend.