President Donald Trump piled pressure yesterday on the woman accusing his Supreme Court pick of sexual assault by insisting that she testify next week if she wants to be heard.

Trump echoed Republican leaders in suggesting that time is running out for Christine Blasey Ford, the California psychology professor whose allegation that she was assaulted as a teenager threatens to derail confirmation of conservative Judge Brett Kavanaugh to America's highest court.

Ford has backtracked from earlier statements that she is ready to face a grilling in the Senate Judiciary Committee. Instead, she is calling for an FBI probe into her allegation that Kavanaugh pinned her to a bed and muffled her cries as he tried to pull off her clothes when she was 15 and he was 17.

Kavanaugh, now 53, denies any such incident took place and no other direct witnesses have come forward.

Trump told journalists at the White House that he retained full faith in the judge, saying it was "very hard for me to imagine that anything happened."

He urged Ford to take her chance at the committee hearing set for Monday, where Kavanaugh is likewise invited to explain his side of the story.

Trump indicated that his patience is wearing thin, even telling political website The Hill that the scandal resembles what he called "the witch hunt" by a special prosecutor into allegations his campaign colluded with Russia to bring about his surprise 2016 election.

"We continue to give her a lot of time. We've held up the whole hearing," Trump told reporters.

The Republican chairman of the Senate committee, Chuck Grassley, wrote to Ford's lawyers, ruling out any FBI role and saying that the sole venue for airing the allegations would be the Senate hearing.

"You have stated repeatedly that Dr Ford wants to tell her story. I sincerely hope that Dr Ford will accept my invitation to do so, either privately or publicly, on Monday," Grassley said.

Late Wednesday, a lawyer for Ford, Lisa Banks, was quoted by The Washington Post saying that the "rush to a hearing is unnecessary and contrary to the Committee discovering the truth."

But Susan Collins, a Republican senator seen as potentially voting against party lines, also said that Ford needed to testify.

"I think it's not fair for Judge Kavanaugh for her not to come forward and testify," she said.

Ultimate goal

Until last week, Kavanaugh looked almost certain to win confirmation in the Senate in a victory for Trump that would tilt the Supreme Court to conservative rulings, potentially for decades to come.

The scandal, erupting just before the Senate Judiciary Committee had been due to vote on Kavanaugh, ignited an uproar fueled by the #MeToo movement against sexual harassment.

For Democrats hoping to hurt Trump before November congressional elections, when they hope to retake at least one house of the Republican-dominated Congress, the row is a godsend.

And Trump -- who faces a raft of serious allegations of sexual impropriety and was once caught on tape boasting of being able to "grab" women's genitals whenever he wanted -- has had to tread a fine line.

Instead of the real estate tycoon's usually no-holds-barred combative style, honed during decades of cutthroat business deals, he has been careful to speak about Ford with respect.

However, he has at the same time repeatedly insisted on Kavanaugh's "unblemished" record.

On Wednesday, Trump made clear that his main goal is shifting the Supreme Court to the right.

"When I first decided to run, everybody said the single most important thing you do is the Supreme Court justice," he said.

Call for FBI involvement

Lawyers for Ford, 51, say now that they want a broader FBI investigation first, rather than a one-day hearing which Democrats say will be used by Republicans as fig leaf before going ahead with Kavanaugh's confirmation vote.

In a letter to the Senate Judiciary Committee, the lawyers said she has faced "vicious harassment and even death threats" since going public with her allegations on Sunday.

"As a result of these kind of threats, her family was forced to relocate out of their home," they added.

Some on the left believe that Ford could become a new icon of the #MeToo campaign against the sexual harassment of women by powerful men. However, with her yet to appear in public, it remains uncertain what level of grassroots anger is being stirred.

A GoFundMe campaign for aiding Ford's costs had raised $135,542 of its $175,000 goal in less than 24 hours Wednesday, although another campaign had raised only around $5,000 after two days.