The search for one terrorist could cause the government to look at phone call records involving millions of Americans.

(L-R) Deputy Attorney General James Cole, Deputy Director of the National Security Agency John Inglis, General Counsel in the Office of the Director of National Intelligence Robert Litt, and Deputy Director of the Federal Bureau of Investigation Sean Joyce (Alex Wong/Getty Images)

The government is acknowledging today that it uses what it calls "hop analysis" -- in which the National Security Agency looks not only at the records of a terror suspect, but also everyone he calls, and everyone who calls those people, and everyone who calls those people.

The disclosure came as members of President Barack Obama's national security team told a Senate panel that they need to be able to keep conducting the surveillance.

But in testimony to the Senate Judiciary Committee, they acknowledged that some limits appear inevitable. They said they want to work with lawmakers who seem intent on imposing those limits.

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