BALANCE BETWEEN PRIVACY AND SECURITY

President Barack Obama has defended the sweeping government surveillance of Americans' phone and Internet activity, calling it a "modest encroachment" on privacy that was necessary to defend the United States from attack.

However, Obama also said he welcomed public debate on the balance between privacy and security.                

"The president has said he welcomes a public debate. It would be odd to say that and then expect a state secret privilege," said Jameel Jaffer, one of the ACLU lawyers on the suit.

The rights group asked the court to immediately halt the NSA's vast tracking program of telephone calls, declare the program illegal, and order the government to purge all databases of the call records.

The government "vacuums up information about every phone call placed within, from, or to the United States," the ACLU said, arguing that it violates the First Amendment rights of free speech and the right of privacy protected by the Fourth Amendment of the US Constitution.

The suit cited the government's acknowledgement that the Foreign Intelligence Surveillance Court required Verizon Business Network Services to turn over metadata about the calls made by each of its subscribers over a three-month period as a continuation of a program that members of Congress said has been in place for seven years.

As a Verizon subscriber, the ACLU named itself as a plaintiff, saying the government's secret monitoring program was "likely to have a chilling effect on whistleblowers and others who would otherwise contact plaintiffs for legal assistance."

The ACLU, the New York Civil Liberties Union and both of their foundations were named as plaintiffs.