Obama: Phone, Internet surveillance has 'saved lives'

President Obama escalated his administration's defense of controversial surveillance programs, claiming Wednesday that the efforts have "saved lives."

The president addressed what has become a global controversy after his NSA director and other top officials told Congress a day earlier that the surveillance system has helped avert "potential terrorist events" more than 50 times since the 2001 terror attacks.

Obama, speaking Wednesday morning during a press conference in Berlin alongside German Chancellor Angela Merkel, affirmed that number. He insisted the tracking of phone calls and Internet data is done in a way that protects civil liberties while keeping Americans safe.

"This is a circumscribed, narrow system directed at us being able to protect our people" under court supervision, he said. "And as a consequence, we've saved lives."

He repeated that "lives have been saved."

The administration so far has provided a limited amount of detail on the individual plots that were averted. Officials have described four of them, including the 2009 plot to bomb the New York subway system. Officials, at a hearing Tuesday, also said the surveillance helped avert a "nascent" plot to bomb the New York Stock Exchange.

Lawmakers are expected to be briefed on dozens of other plots on Wednesday, and so more information will likely trickle out to the public.

Still, revelations earlier this month about the National Security Agency's extensive effort to monitor -- but not listen in on -- phone calls and Internet communications have sparked concerns that the government is going too far.

Some question whether the plots that were disrupted could have been tracked in another way.

Obama said Wednesday he thinks the administration has "struck the appropriate balance." He reiterated that nobody is listening to calls without a warrant and that, with the Internet surveillance program, officials are only following specific leads under court supervision.

"This is not a situation in which we are rifling through the ordinary emails of German citizens or American citizens or French citizens or anybody else," he said.