Democratic presidential candidate Hillary Clinton has agreed to testify on Capitol Hill this month about two controversial issues when she was secretary of state -- the fatal terror attacks in Benghazi, Libya, and using a private server and emails for official business, her attorney said Tuesday.

Attorney David Kendall said his client can appear before the House Select Committee on Benghazi as early as May 18.

In a letter to committee Chairman Trey Gowdy, R-S.C., Kendall said Clinton will testify “as long as possible” but made clear she won’t make separate appearances to testify about the two issues, as requested.

“The committee has consistently shown it is interested in getting the facts and doing so in a deliberate and diligent manner,” said committee spokesman Jamal D. Ware, who also made clear the offer to testify is still being considered.

“Chairman Gowdy should take yes for an answer and finally schedule the hearing,” said Maryland Rep. Elijah Cummings, the top Democrat on the committee. “Dragging out this process further into the presidential election season sacrifices any chance that the American people will see it as serious or legitimate.”

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It remains unclear whether Clinton, a former first lady and U.S. senator from New York, will testify in a closed or open hearing before the special committee, formed to investigate the events surrounding the Sept. 11, 2012, Benghazi attacks in which U.S. Ambassador Chris Stevens and three other Americans were killed.

Obama administration officials said in the early aftermath that the attacks were sparked by an anti-Islamic video but later acknowledged they were terror-related.

Clinton has already testified on the issue, answering such questions as whether adequate security was in place before the attacks and about the extent of U.S. intelligence about a possible attack.

“As you know, Secretary Clinton testified more than five hours before committees in both the House and Senate about the tragic events in Benghazi,” Kendall wrote. “Secretary Clinton remains ready to address whatever additional questions this committee may have.”

Cummings also said in his response that “we have still found not a scrap of evidence to support claims Secretary Clinton ordered a stand-down, approved an illicit weapons program, or any of the other wild allegations that Republicans have been making about her."

While Clinton’s role in the Benghazi incident is expected to remain an issue with some voters through the election cycle, the server and email issue has created problems for the early Clinton campaign.

News reports last month revealed that Clinton sent or received roughly 60,000 private emails while the country’s top diplomat from 2009 to 2013. However, she erased half of them, which she deemed private.

“Secretary Clinton is ready totestify in a public hearing at any time,” a spokesperson said Tuesday. “Given the fact that she has already testified previously on this very matter, the only reason the committee might seek to further prolong this inquiry would be to again exploit a tragedy for purely political purposes.”

Fox News' Chad Pergram contributed to this report.