Clinton to testify on Benghazi report on December 20

U.S. Secretary of State Hillary Clinton speaks during a news conference at Stormont Castle in Belfast December 7, 2012.

WASHINGTON (Reuters) - U.S. Secretary of State Hillary Clinton will testify on December 20 before the House of Representatives and Senate foreign affairs committees on a report on the deadly attack on the U.S. diplomatic post in Benghazi, Libya, the committees said on Wednesday.

The attack on September 11 killed U.S. Ambassador Christopher Stevens and three other Americans, and raised questions about the adequacy of security in far-flung posts.

Republicans have criticized Democratic President Barack Obama's administration for its flawed early public explanations of the attack.

They have also criticized shifting explanations of why talking points given to U.S. Ambassador to the United Nations Susan Rice were changed to delete a reference to al Qaeda. Some Republicans have used that criticism to question Rice's suitability as a candidate to replace Clinton, if Obama were to nominate her.

Clinton has said she planned to retire from her post at State after Obama's first term.

An accountability review board convened by the State Department is expected to release a report on the Benghazi attack before Clinton testifies.

The board, led by veteran diplomat Thomas Pickering, is expected to consider whether enough attention was given to potential threats and how Washington responded to security requests from U.S. diplomats in Libya.

Democratic Senator John Kerry, chairman of the Senate Foreign Relations Committee, said in a statement: "We ask our diplomats and development personnel to operate in some of the most dangerous places on the planet. We owe it to them, and we owe it to the memory of Ambassador Chris Stevens and his three fellow Americans who lost their lives in Benghazi to get past the politics and focus on the substance of what happened and what it tells us about diplomatic security going forward."

(Reporting by Patricia Zengerle and Arshad Mohammed; Editing by Stacey Joyce)