Washington (CNN) Former Secretary of State Hillary Clinton has agreed to testify to the House's select committee investigating Benghazi, the panel's Democratic ranking member told CNN on Tuesday.

Rep. Elijah Cummings said that Clinton agreed to testify before the committee investigating the 2012 terrorist attack in December after he contacted her months earlier.

"The chairman asked me back in September to inquire as to whether Secretary Clinton would testify," Cummings said. "She immediately said she would and that she wanted to come in December, but if December did not work, she would come in January. She said I'll do it, period. The fact is she was very clear. She did not hesitate for one second."

The U.S. consulate in Libya was attacked on Sept. 11, 2012. Four Americans, including the U.S. Ambassador to Libya Chris Stevens, were killed. Initially, the attack was thought to be perpetrated by an angry mob responding to a video made in the U.S. which mocked Islam and the Prophet Mohammed, but was later determined to be a terrorist attack.

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