The exchange came at a Senate Intelligence Committee hearing before the phone program had been divulged.
"Does the NSA collect any type of data at all on millions or hundreds of millions of Americans?" Wyden, D-Ore., asked Clapper.
"No, sir," Clapper answered.
"It does not?" Wyden pressed.
Clapper reluctantly softened his answer somewhat: "Not wittingly," he said. "There are cases where they could, inadvertently perhaps, collect — but not wittingly."
Turns out they do file away phone records — not conversations, but the phone numbers of calls placed and received — on millions of Americans.
After that leaked to the public, Clapper tried to explain his answer in an NBC News interview. "I responded," he said, "in what I thought was the most truthful, or least untruthful manner."
Wyden says he even gave Clapper a day to prepare his answer. And, Wyden says, he gave Clapper a chance to change his answer in private.
CONFUSION IN CONGRESS
Even one of the surveillance programs' staunchest supporters had trouble keeping the basics straight.
Explaining the programs to reporters, Sen. Lindsey Graham, R-S.C., initially described how the NSA uses pattern analysis to sort through millions of phone calls from the United States.
"You basically say, 'Computer, tell me who has called Yemen once a week for the last month,' " Graham said. "They spit out a bunch of numbers."
But intelligence officials say that doesn't happen.
They say Americans' phone records are only accessed if there is evidence connecting them to suspected terrorists — not just a pattern of calls, such as to a certain country.
After intelligence officials objected, Graham — a member of the Armed Services and Judiciary committees but not the Intelligence panel — said he had misspoken.
But his earlier words reflect privacy advocates' fears about the sort of thing the government might do with its library of call records, if not now then maybe someday in the future.
The president tried to reassure Americans about the massive surveillance programs. But he left some misimpressions.
"With respect to the Internet and emails," Obama said, "this does not apply to U.S. citizens."
Indeed, intelligence agency leaders say that these programs can't legally target Americans. That doesn't mean their online activities won't be swept up in the surveillance net, however.
Analysts watching a suspected terrorist see that person's emails, Facebook friends and other online traffic that might include Americans.
And American communications can be accidentally captured by computer programs searching for data on terror suspects. John Negroponte, a former director of national intelligence, said such unintentionally gathered information wouldn't be kept or used by agents.
Some Congress members bristled at the way Obama described briefings available to them: "Your duly elected representatives have been consistently informed on exactly what we're doing," he said.
Sen. Mike Johanns, R-Neb., said: "The impression has been created that people (are) parked in our office giving us daily briefings on this, or monthly briefings. And that's not been the case."
At a Senate hearing Wednesday, Johanns complained: "We're all getting bombarded with questions that many of us at the rank-and-file level in the Senate cannot answer."
Associated Press writers Adam Goldman, Eileen Sullivan, Lara Jakes, Matt Apuzzo, Donna Cassata and Kimberly Dozier contributed to this report.
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