The head of the National Security Agency has defended US surveillance programs as part of a "noble" mission to protect the nation and says reports on them are "sensationalised".
"The future of this country depends on our ability to defend against cyber attacks and terrorist threats, and we need the tools to do it," said General Keith Alexander, chief of the NSA.
The agency heads the PRISM program and other vast data collection efforts revealed in recent months by former US intelligence contractor Edward Snowden.
Alexander, speaking at the Billington Cybersecurity Summit in Washington on Wednesday, said there have been relatively few terror attacks on US soil since September 11, 2001 despite growing threats around the world.
"This is not by accident. It's by a lot of hard work," he said.
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"Twenty-two cryptologists lost their lives in Iraq and Afghanistan. They're the heroes, not the (people behind) media leaks."
Alexander appealed to the public to support the surveillance effort, which is coming under scrutiny in Congress, and argued that the facts about the programs have been distorted.
"It's been sensationalised and inflamed in much of the reporting," he said.
"What's hyped up in a lot the reporting is that we are listening to your conversations, that we're reading your emails. That's not true... We understand our job is to defend this country. It's a noble mission."
Alexander repeated his assertion that more than 50 terrorist threats around the world have been foiled as a result of the intelligence gathered from the programs, which have been harshly criticised by US allies ranging from Germany to Brazil.
The NSA has been in the centre of a firestorm since the Snowden leaks, which revealed wide-ranging programs which scoop up data on telephone calls and Internet activity.
