Christine Blasey Ford wants the FBI to investigate her allegation that she was sexually assaulted by US Supreme Court nominee Brett Kavanaugh before she testifies at a Senate Judiciary Committee hearing next week, her lawyers have written in a letter.

The lawyers wrote that Ms Ford, who is now a college professor in California, wants to cooperate with the panel.

But in the days since she publicly accused Kavanaugh of the assault when they were teens at a party 35 years ago, she has been the target of “vicious harassment”

Her family has relocated, they said.

Ms Ford’s attorney told CNN her client has been “deflecting death threats and harassment”.

An FBI investigation “should be the first step in addressing the allegations,” the lawyers wrote in the letter, which was obtained by The Associated Press.

The development comes as President Donald Trump showered sympathy on his embattled Supreme Court nominee and as Senate Republicans and Democrats fought determinedly over who should testify at a high-stakes hearing on the allegation just six weeks before major congressional elections.

Democrats have said they wanted more time for the FBI to investigate – and more witnesses besides Mr Kavanaugh and Ms Ford, hoping to avoid what would turn into merely a “he-said-she-said” moment.

Those witnesses would include Kavanaugh’s high school friend Mark Judge, who Ms Ford said was in the room when she was assaulted, but Judge said no.

Mr Kavanaugh has denied Ms Ford’s allegation, and Judge says he doesn’t remember any such incident.

The lawyers for Ford predicted the hearing, as now scheduled, “would include interrogation by senators who appear to have made up their minds” that she is “mistaken” and mixed up.

Donald Trump is looking for a second Supreme Court appointee. Photo: Getty

The furious jockeying over her testimony underscores the political potency so close to an election that will decide control of both the House and Senate, not to mention the confirmation of a conservative justice likely to serve on the high court for decades.

Ms Ford, a psychology lecturer, has accused Mr Kavanaugh of drunkenly trying to remove her clothing in 1982 when they were both teenagers in a Washington DC suburb.

Mr Trump, who reportedly did not meet Mr Kavanaugh on Tuesday, expressed sympathy for his nominee.

“I feel so badly for him that he’s going through this, to be honest with you,” the Mr Trump told a news conference, the BBC reported. “This is not a man that deserves this.

Hopefully the woman will come forward, state her case. He will state his case before representatives of the United States Senate. And then they will vote.”

Earlier, committee chairman Chuck Grassley said Professor Ford had not responded to attempts by the Republican-led Senate Judiciary Committee to contact her about appearing at a hearing set for Monday.

Senator John Cornyn, a member of the Senate Republican leadership, appeared to cast doubt on Ms Ford’s allegations.

“We just don’t know what happened 36 years ago and there are gaps in her memory,” Senator Cornyn told reporters.

“She doesn’t know how she got there, when it was, and so that would logically be something where she would get questions.”

Senator Cornyn’s fellow Republicans have generally avoided criticising Professor Ford, instead castigating Democrats for not revealing her allegations earlier.

-With AAP, ABC