Eric Nordstrom, who was the regional security officer in Libya, also referenced a State Department document that detailed 230 security incidents in Libya between June 2011 and July 2012 that demonstrated the danger to Americans.
Stevens and three other Americans were killed at U.S. diplomatic facilities in Benghazi, Libya, on Sept. 11. U.S. officials initially described the attack as a spontaneous protest, but later called it terrorist act.
Nordstrom is among the witnesses to testify Wednesday before the House Oversight and Government Reform Committee. According to the panel's chairman, Rep. Darrell Issa, R-Calif., and the head of a subcommittee, Rep. Jason Chaffetz, R-Utah, the State Department refused repeated requests to provide more security for U.S. diplomats in Libya.
Nordstrom's Oct. 1 email referred to his earlier communications with superiors at the State Department and indicates the department turned down his pleas.
"You will note that there were a number of incidents that targeted diplomatic missions and underscored the GoL's (Government of Libya) inability to secure and
"This was a significant part of (the diplomatic) post's and my argument for maintaining continued DS (diplomatic security) and DOD (Department of Defense) security assets into Sept/Oct. 2012; the GoL was overwhelmed and could not guarantee our protection.
"Sadly, that point was reaffirmed on Sept. 11, 2012, in Benghazi," he added.
Nordstrom said the incidents demonstrated that security in Libya was fragile and could degrade quickly. He added that Libya was "certainly not an environment where (the diplomatic) post would be directed to 'normalize' operations and reduce security resources in accordance with an artificial time table."
Nordstrom also said that diplomats in Libya were told not to request an extension of a 16-member special operations military team that left in August, according to an official of the Oversight panel. The official spoke on condition of anonymity because they were not authorized to discuss the matter publicly.
The State Department has said it never received a request to extend the military team beyond August, and added that its members were replaced with a security team that had the same skills.