(CNN)Sen. Dianne Feinstein, the California Democrat who has come under sharp scrutiny for her handling of the sexual assault accusations against Brett Kavanaugh, said Monday that she had privately held on to a letter detailing the allegations because the accuser had asked her to keep them confidential.

But it was a news report last week that ultimately forced her hand, even as she struggled to explain the chain of events in brief interviews on Monday.

"She had asked to remain confidential," Feinstein, the top Democrat on the Senate Judiciary Committee, said on her way to Senate votes.

Feinstein waited until late last week to provide the letter to the FBI -- only after a news report surfaced detailing the existence of the letter. Feinstein, aides said, wanted to protect the identity of the accuser, Christine Blasey Ford. An attorney for Ford said she did not want to subject herself to the "very brutal" confirmation process -- but agreed to do so and reveal herself publicly to The Washington Post after the report surfaced.