By Mark Hosenball
WASHINGTON (Reuters) - Sidney Blumenthal, a longtime friend of Hillary Clinton who was an unofficial adviser while she was secretary of state, promised to cooperate with a congressional committee investigating the deadly 2012 attacks in Benghazi, Libya.
Blumenthal, a former senior adviser on President Bill Clinton's White House staff, sent private intelligence reports on Libya, prepared by a former senior CIA officer, to Hillary Clinton before and after the attacks, which killed the U.S. ambassador and three other Americans.
Congressional investigators have issued a subpoena calling Blumenthal to testify before the U.S. House of Representatives Select Committee on Benghazi, which is probing the attacks.
"I have informed the House Select Committee on Benghazi that I will cooperate with its inquiry and look forward to answering the committee’s questions,” Blumenthal said in a statement issued through his lawyer on Thursday.
Democrats say Republicans are using the committee to try to discredit Clinton as she runs for president in 2016.
The State Department said it would release at 12:30 p.m. on Friday some 300 Clinton emails about Libya, which will include but go beyond her correspondence with Blumenthal, which could complicate Clinton's White House campaign.
The State Department said the emails that will to be made public "do not change the essential facts or our understanding" of the Benghazi incident.
Clinton's emails, sent or received on a private account she created and ran through a server based in her home, could provide fodder for Republicans eager to show that Clinton mismanaged security at a U.S. diplomatic facility and nearby CIA base in Libya and then tried to spin the consequences to her political advantage.
This week, the New York Times published emails from Clinton showing that she passed on some of the private intelligence reports she received from Blumenthal to close aides and other U.S. officials, including Chris Stevens, the U.S. Ambassador to Libya who died in the attacks.
The message traffic has raised questions about whether Blumenthal or his associates were trying to promote business interests in Libya, a charge people close to Blumenthal have denied.
Blumenthal said he had sent Clinton memos as a private citizen.
"From time to time, as a private citizen and friend, I provided Secretary Clinton with material on a variety of topics that I thought she might find interesting or helpful. The reports I sent her came from sources I considered reliable," Blumenthal said in the statement.
(Writing by Alistair Bell; Editing by Jonathan Oatis)