"To this day, to this day, we do not have a complete picture," Clinton said. "We do not have all the answers, no one in this administration has ever claimed otherwise."
"Every one of us has made clear that we are providing the best information we have at that time and that information continues to be updated, it also continues to be put into context and more deeply understood through the process we are engaged in," she said.
Susan Rice, the U.S. ambassador to the United Nations, has come in for particularly withering criticism from Republicans for asserting on Sunday morning talk shows that preliminary intelligence indicated that well-armed extremists hijacked a protest against the film to attack the consulate.
Several senior State Department officials have said they had never concluded that was the case even though it was the early assessment from the intelligence community.
Republicans have suggested that the administration was trying to cover up the real reason for the attack, which they say was a pre-meditated strike against the United States on the 11th anniversary of the Sept. 11, 2001 terrorist attacks in the United States.
"Ambassador Rice had the same information from the intelligence community as every other senior official did," Clinton said. "We can only tell you what we know based on our most current understanding of the attack and what led up to it. Obviously, we know more as time goes by and we will know even more than we did hours and days after the attack."
There are three separate investigations into the attack going on now: an FBI probe into the deaths of the four Americans, an independent inquiry by a panel appointed by Clinton and the congressional hearings.
Clinton urged caution and patience in dealing with partial accounts.
"I want us to keep in mind that four Americans were killed, four men who served our country," she said. "Dozens of Americans fought for their lives that night, and to honor them we all have to get to the bottom of every question and answer it to the best of our ability."
"And then we have to be sure that we apply the lessons we learned to make sure that we protect everybody in harm's way."