SAN JOSE, California (AP, AFP) - President Barack Obama is defending his government's secret surveillance, saying Congress has repeatedly authorized the collection of Americans' phone records and foreigners' internet use.

In his first comments since the programs were publicly revealed this week, Mr Obama mounted a staunch defense on Friday of just the exposed spy agency surveillance programs, saying they were legal and telling Americans "nobody is listening to your telephone calls."

Mr Obama also said there was a tradeoff to be made between national security and people's privacy, though said it was right that the exact balance between the two should be publicly debated.

He added that internet targeting is aimed at foreign nationals, not American citizens.

Mr Obama said he increased some of the "safeguards" on the programs after taking office. And he believes they help his administration stop terrorist attacks.