Hillary Rodham Clinton’s lawyer on Monday told the congressional committee investigating the 2012 attacks in Benghazi, Libya, that Mrs. Clinton would testify before the panel only once, and that she was willing to do so in two weeks.

The committee’s chairman, Trey Gowdy, Republican of South Carolina, has said that he wants Mrs. Clinton to testify twice — once about the attacks and again about her use of a personal email account to conduct government business when she was secretary of state.

But Mrs. Clinton’s lawyer, David Kendall, said there was “no basis, logic or precedent for such an unusual request.”

“The secretary is fully prepared to stay for the duration of the committee’s questions on the day she appears,” Mr. Kendall said, adding that Mrs. Clinton, who is running for president, was prepared to testify the week of May 18 or later.

“Members of the committee are able to decide how much they will focus on the tragic deaths of four Americans in Benghazi, including what can be done to keep those who serve our country safe, and how much they will focus on how she emailed,” Mr. Kendall said.

A spokesman for the committee, Jamal D. Ware, issued a statement saying that the committee was considering Mr. Kendall’s offer and that Mr. Gowdy would comment later “regarding the path forward.”