U.S. intelligence committees open Benghazi attack probe By Susan Cornwell and Tabassum Zakaria WASHINGTON (Reuters) - U.S. intelligence and State Department officials testified behind closed doors on Capitol Hill on Thursday about the attack on the U.S. diplomatic mission in Benghazi, Libya, that has turned into a contentious issue between Republicans and the administration of President Barack Obama. Former CIA Director David Petraeus, before his resignation last week over an extramarital affair, had initially been scheduled to testify at Thursday's closed Senate and House of Representatives intelligence committee hearings, but will now be a solo witness before those panels on Friday morning. Republicans have accused the Obama administration of misinformation in the early days following the September 11, 2012, attack that killed the U.S. ambassador to Libya and three other Americans. Administration officials say their initial comments that it appeared the attack grew spontaneously out of protests over an anti-Muslim film rather than a premeditated strike were based on the best available information at that time. Two top Republican senators on Wednesday threatened to block any nomination of Susan Rice, U.S. ambassador to the United Nations, to a Cabinet post, which must be confirmed by the Senate, for making those initial comments. Obama came to her defense and said if she was the right person for a spot in his Cabinet, he would nominate her. Secretary of State Hillary Clinton will testify before Congress about the Benghazi attack after a State Department report is completed, likely in December. On Thursday, Director of National Intelligence James Clapper, acting CIA Director Michael Morell, National Counterterrorism Center Director Matthew Olsen, FBI Deputy Director Sean Joyce and Under Secretary of State for Management Pat Kennedy were testifying behind closed doors at separate hearings of the House and Senate intelligence committees. Clapper and Kennedy walked past a throng of reporters without making any comment before entering a basement hearing room that is specially reserved for the House intelligence committee. A red sign on the door says "restricted area." The House Committee on Foreign Affairs was holding an open hearing with non-government experts on the Benghazi attack on Thursday. The coordinated, preplanned and brazen attack against the U.S. consulate in Benghazi on September 11th was an outrage. Also disgraceful is the sad parade of conflicting accounts of the attack that we have received from Administration officials in the weeks and months since," Republican Representative Ileana Ros-Lehtinen, chairwoman of the House Foreign Affairs Committee, said in a statement. "Successive revelations in public reports indicate that the Administration failed to adequately protect the American consulate and denied consulate requests for additional security," she said. Editing by Warren Strobel and Eric Beech