Supreme Court nominee Judge Brett Kavanaugh appears before the Senate Judiciary Committee during his Supreme Court confirmation hearing in the Hart Senate Office Building on Capitol Hill September 4, 2018 in Washington, DC.

Christine Blasey Ford, who accuses Supreme Court nominee Brett Kavanaugh of sexually assaulting her when they were teens, has yet to confirm she will testify before the Senate Judiciary Committee, according to Sen. Chuck Grassley, the panel's Republican chairman.

"We have reached out to her in the last 36 hours three or four times by email, and we have not heard from them," Grassley said Tuesday morning on conservative commentator Hugh Hewitt's radio show. "So it kind of raises the question, do they want to come to the public hearing or not?"

Asked about the chairman's claim, a spokesman for the Judiciary Committee's ranking Democrat, Sen. Dianne Feinstein, told CNBC: "It could be that they haven't heard from her yet because they scheduled the hearing without first talking with her or her lawyer."

Feinstein had received a letter from Ford in late July alleging that Kavanaugh had drunkenly held her down on a bed and attempted to take her clothes off when they were in high school in the 1980s. Kavanaugh's friend, Mark Judge, was in the room as well, and jumped on them, according to Ford.

Kavanaugh, President Donald Trump's second pick for a lifetime appointment to the Supreme Court, has denied the allegation.

In a letter to The Washington Post sent through a lawyer Tuesday, Judge said that he has "no memory of this alleged incident" and that he does "not recall the party" Ford described.

He added: "I do not wish to speak publicly regarding the incidents described in Dr. Ford's letter."

Grassley had originally opposed scheduling a public hearing before the 21-member committee, saying in a statement that the "standard procedure" would be to set follow-up calls with Kavanaugh, 53, and Ford, 51.

The Republican-controlled committee had recently completed Kavanaugh's heated and highly politicized judicial hearings, and was set to vote Thursday to push Kavanaugh's nomination toward confirmation.

But Democrats and Republicans, including crucial swing vote Sen. Susan Collins, R-Maine, called for a hearing. Both Kavanaugh and Ford, through her attorney, said they would be willing to defend their positions in public testimony. Grassley scheduled the hearing for Monday.

But as of Tuesday morning, Grassley said in the radio interview, neither Ford nor her lawyer, Debra Katz, had confirmed her attendance.

"We're delaying the vote strictly to get all the facts out on the table," Grassley said.

Katz did not respond to CNBC's requests for comment on Grassley's claim.

Collins said Monday that Kavanaugh would "obviously" be disqualified from the high court if he lied in denying Ford's allegation, and called for a public hearing.

"I really hope that she doesn't pass up that opportunity," Collins said Tuesday. Later, the Maine Republican called on committee leaders to let Ford's and Kavanaugh's legal counsel question each other during the hearing before allowing senators to pose their own questions.

Later Tuesday morning, Feinstein blasted Grassley's proposed hearing, which is so far only set to include Kavanaugh and Ford as witnesses, as insufficient.

"Chairman Grassley today said there would be only two witnesses invited to testify at the Kavanaugh hearing next week on sexual assault allegations. Compare that with the 22 witnesses at the 1991 Anita Hill hearing and it's impossible to take this process seriously," Feinstein said.

"This is another attempt by Republicans to rush this nomination and not fully vet Judge Kavanaugh," the California Democrat added.

— CNBC's Tucker Higgins and Brian Schwartz contributed to this article.