Stephanie O'Sullivan, nominated by President Barack Obama to the country's second-highest intelligence job, told the Senate Intelligence Committee that the administration was warned "at the end of last year."
"We have warned of instability," said O'Sullivan, currently the associate deputy director of the Central Intelligence Agency.
But Senator Dianne Feinstein, the committee chairperson, expressed doubts about the ability of the CIA and others to quickly inform the president, the secretary of state, and Congress of threats.
"I have doubts as to whether the intelligence community has lived up to its obligations in the area," she said.
The California Democrat told journalists afterward that she has noted gaps in the collection of information from social networking sites, including Facebook, in the buildup to the Egypt crisis.
"I've looked at some intelligence in this area, which indicates some lacking," she said. When asked, she specified a lacking of "collection" of information.
"It's very concerning. Maybe the CIA doesn't consider that it should be collecting open-source data, but my view is that open-source data can be very, very important."
That type of information, she said, should be given "considerable deference."
"So we need to uncover more of this and we certainly will."
O'Sullivan, nominated to become deputy director for National Intelligence under director James Clapper, has 30 years experience in the US intelligence community.
"The events in Egypt are rapidly unfolding and we're working to track them on the ground," she said.
Senator Saxby Chambliss, the highest-ranking Republican on the Democratic-controlled committee, asked O'Sullivan to provide in the coming days a more precise timeline of when intelligence officials learned of the threat to the regime of Egyptian president Hosni Mubarak.
Mubarak, who has vowed not to stand in upcoming elections, has come under increasing pressure from the United States and western nations to step down amid days of violent protests against his 30-year rule.