The State Department said Monday that Secretary of State Hillary Rodham Clinton will testify before Congress about security failures in the Sept. 11 terrorist attack on the U.S. Consulate in Benghazi, Libya.

“She will testify while she is still sitting secretary of state,” State Department spokeswoman Victoria Nuland said of Mrs. Clinton, who is slated to step down in the coming weeks, pending Senate confirmation of Sen. John F. Kerry, Massachusetts Democrat, as her replacement.

The Senate Foreign Relations Committee, which Mr. Kerry currently chairs, has not yet set dates for his confirmation hearing, which is expected to proceed smoothly.

Mrs. Nuland said that Mrs. Clinton has been speaking on the telephone with Mr. Kerry “virtually nonstop” lately.

“She is 100 percent committed to having the smoothest possible transition, to helping him as much as possible, and she’ll be available as much as he needs her,” Mrs. Nuland said, adding that when Mrs. Clinton will testify on Benghazi is being arranged as the newly elected 113th Congress is just gearing up.

“We have a new Senate Foreign Relations Committee,” she said. “So we’re working now with the committee on scheduling of both the Benghazi hearing [and] the confirmation hearing, getting the sequence agreed with them.”