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Secretary of State John Kerry has offered to testify before the House Oversight Committee on Government Reform on the 2012 attack on the U.S. mission in Benghazi, Libya, according to a letter sent to Oversight Committee chairman Darrell Issa (R-Calif.) today.

The letter offered two dates on which Kerry could testify, June 12or June 20.

Issa had subpoenaed Kerry twice to appear before the committee, once on May 21 and a second time on May 29. State Department officials said that Kerry was unavailable on either of those dates.

The letter, written by State Department Assistant Secretary for Legislative Affairs Julia Frifield, asks Issa to withdraw the second subpoena.

"We were surprised that after initially issuing a subpoena on May 1 and subsequently withdrawing it, you felt it was necessary to issue a second subpoena commanding the Secretary to appear on May29," Frifield wrote. "We ask that the Committee withdraw its subpoena for May 29 and work with the Department to find a more appropriate hearing date."

Spokesperson Marie Harf said Kerry's cooperation with the House Oversight Committee means he will not testify before a separate select committee, chaired by Rep. Trey Gowdy (R-S.C.), also focused on Benghazi.

"He will appear once on Benghazi," Harf said.