US PRESIDENT Donald Trump has been slammed for mocking alleged sexual assault survivor Christine Blasey Ford days after he called her "a very fine woman".

Mr Trump ignited a crowd at a campaign rally in Mississippi by mocking Dr Ford who has claimed she was sexually assaulted by Supreme Court nominee Brett Kavanaugh decades ago.

The audience laughed as Mr Trump ran through a list of what he described as holes in Dr Ford's testimony before the Senate Judiciary Committee.

She testified that Kavanaugh pinned her on a bed, tried to take off her clothes and covered her mouth in the early 1980s, when the two were teenagers. Mr Kavanaugh has denied Dr Ford's allegations.

"How did you get home? 'I don't remember,"' Mr Trump said at the rally in Southaven. "How did you get there? 'I don't remember.' Where is the place? 'I don't remember.' How many years ago was it? 'I don't know. I don't know. I don't know."'

Imitating Ford, he added, "But I had one beer - that's the only thing I remember."

It marked the sharpest criticism by Mr Trump of Dr Ford since she came forward publicly with the allegation last month.

He had previously called Dr Ford a "very credible witness."

Dr Ford's lawyer Michael Bromwich called Mr Trump's attack "vicious, vile and soulless."

"Is it any wonder that she was terrified to come forward, and that other sexual assault survivors are as well?" Mr Bromwich tweeted. "She is a remarkable profile in courage. He is a profile in cowardice."

Arizona Republican Senator Jeff Flake said that mocking "something this sensitive at a political rally is just not right".

"I wish he hadn't done it," Sen. Flake said. "It's kind of appalling."

Flake is a key Republican vote in the confirmation battle, and while he said last week he would vote to confirm Kavanaugh, he also called for an expanded FBI investigation that resulted in a one-week delay.

Sen. Flake has not said how he will vote if the nomination comes up this week.

His Republican colleague Susan Collins joined in with criticism of the president, saying his comments were "just plain wrong".

Republican Senator Lisa Murkowski called the comments "wholly inappropriate and in my view unacceptable."

Senators Flake, Collins and Murkowski are potential swing voters on Mr Kavanaugh's confirmation.

Republicans hold a 51-49 majority in the Senate, with Vice President Mike Pence a potential tie-breaking vote, meaning they can only lose one vote on Kavanaugh's nomination.

Actress Alyssa Milano, who came forward as a sex assault survivor last week, led the chorus on Twitter of people who were repulsed by Mr Trump's comments.

Writing to Donald Trump Jr, Milano said: 'Your father is an a**hole. This is the most misogynist display of barbaric insensitivity that I've ever seen. This is why I didn't report [my abuse]. This right here. Women are watching. And we vote.'

Mr Kavanaugh's truthfulness to Congress - including how he represented his alcohol consumption - is also under the microscope, with former Yale classmates accusing the judge of misleading politicians when he said he never experienced blackouts.

That claim was further called into question after the New York Times published a copy of a letter written by Mr Kavanaugh in 1983 where he warned his friends of the danger of eviction from a beachfront condo they had rented for the weekend.

"Warn the neighbors that we're loud, obnoxious drunks with prolific pukers among us. Advise them to go about 30 miles," he wrote.