(CNN) — California Democratic Rep. Ro Khanna is calling for California Democratic Sen. Dianne Feinstein to resign — a rare instance of a lawmaker urging a member of their own party to step down from Congress.

“It’s time for @SenFeinstein to resign. We need to put the country ahead of personal loyalty. While she has had a lifetime of public service, it is obvious she can no longer fulfill her duties. Not speaking out undermines our credibility as elected representatives of the people,” Khanna said Wednesday on Twitter.

The 89-year-old Feinstein announced in early March that she had been hospitalized and was receiving treatment for shingles. On March 7, Feinstein said on Twitter that she was recovering at home as she continued to receive treatment, and she said that she looked forward to returning to the Senate “as soon as possible.”

Multiple sources told CNN there has not been a specific date set for her return to the chamber.

The California Democrat announced in February that she would not run for reelection, but she has not announced when she will return to the Senate.

A number of Democrats have already launched campaigns for Feinstein’s seat in 2024 in what is shaping up to be a competitive primary. Khanna is co-chair of Democratic Rep. Barbara Lee’s campaign to fill Feinstein’s Senate seat.

CNN has reached out to Feinstein’s office to request comment.

Democratic Rep. Dean Phillips responded to Khanna’s tweet saying that he agreed.

“Senator Feinstein is a remarkable American whose contributions to our country are immeasurable. But I believe it’s now a dereliction of duty to remain in the Senate and a dereliction of duty for those who agree to remain quiet,” Phillips tweeted.

Senate Judiciary Committee Chairman Dick Durbin acknowledged to CNN recently that Feinstein’s absence has slowed down their push to confirm nominees.

Asked if her absence has longer ramifications for the Democrats’ ability to confirm nominees, the committee chairman said, “yes, of course it does,” pointing to the long process of getting nominees scheduled for votes during precious floor time.