Recent revelations that the NSA has monitored the cell phones of foreign leaders, including German Chancellor Angela Merkel, came to light from information leaked by former NSA contractor Edward Snowden, who is hiding out under temporary asylum in Russia.
"It is my understanding that President Obama was not aware Chancellor Merkel's communications were being collected since 2002. That is a big problem," she said.
Feinstein said she supported the White House's announcement that phone surveillance of allied leaders will cease but reiterated the need for a full review of all intelligence programs.
But later National Security Council spokeswoman Caitlin Hayden issued a statement that would not confirm that surveillance on all foreign leaders would cease, only that a review on the appropriate posture when it comes to heads of state had been under way since the summer and decisions were still being made.
"The administration's review is ongoing so I'm not in a position to discuss the details or the outcomes, but we have already made some decisions through this process and expect to make more as we continue," Hayden said. "The review is meant to be completed by the end of the year."
Feinstein said that the events dictated a thorough examination of intelligence initiatives.
"As far as I'm concerned, Congress needs to know exactly what our intelligence community is doing. To that end, the committee will initiate a major review into all intelligence-collection programs," she said.
Separately, the Senate Intelligence Committee is scheduled to vote on legislation behind closed doors Tuesday, intended to add greater transparency and accountability to the NSA's domestic surveillance of the phone and Internet records of millions of Americans.
Feinstein has argued that such programs are necessary for national security but favors legislation intended to enhance the program's credibility, such as making clear there are express limits on access to such information.