The incidents weren't intentional and occurred as the agencies conducted electronic surveillance of suspected foreign terrorists, Robert Litt, general counsel for the U.S. national intelligence director, told reporters on a conference call.
The Obama administration is seeking to renew a law providing broad authority to conduct electronic surveillance and is facing resistance from some lawmakers over concern that the communications of Americans have been monitored. The 2008 law updated the Foreign Intelligence Surveillance Act to provide a legal framework for warrantless wiretapping the government began after the terrorist attacks of Sept. 11, 2001.
"There have been some compliance incidents" involving the "incidental collection" of U.S. citizens' communications, Litt said. "The incidents that have occurred have been unintentional, accidental and not reflective of any intent to evade the statute."
The law expires in December, and the House is scheduled to vote Wednesday on a bill that would reauthorize it until the end of 2017.
U.S. intelligence agencies are required to follow procedures to minimize the collection, retention and dissemination of communications involving U.S. citizens. A court-approved warrant is required if a U.S. citizen becomes the target of surveillance.
Litt wouldn't say how many times the communications of U.S. citizens have been monitored.
"This is not something that's reasonably possible to estimate with any degree of accuracy," he said. "In order to do that we'd have to talk about the details of the collection in a way that would compromise national security."
Asked if he knew how many incidents there have been, Litt said, "There are times when somebody in my position likes to stick very closely to the talking points."
In one case, a secret court that oversees the Foreign Intelligence Surveillance Act found an unreasonable collection that violated the Fourth Amendment of the Constitution. Litt wouldn't provide details about the case and said "a solution was found" and the court "subsequently found that the problem had been cured."
Thirteen senators, including Democrat Ron Wyden of Oregon and Republican Rand Paul of Kentucky, sent a letter July 26 to Director of National Intelligence James Clapper asking for an estimate of the number of people located in the United States whose communications have been reviewed.
"We understand that it might not be possible for the intelligence community to calculate this number with precision, but it is difficult for us to accept the assertion that it is not possible to come up with even a rough estimate of this number," the senators wrote.
Wyden has placed a hold on the Senate's bill to reauthorize the law and believes it "needs to be modified to ensure that the privacy of law-abiding American citizens is protected," his spokesman, Tom Caiazza, said in an email Tuesday.
Privacy groups including the American Civil Liberties Union have filed lawsuits claiming the law is unconstitutional and gives the government unchecked powers.
"It's somewhat shocking that four years later Congress is voting on this without real substantial information about how many Americas are being spied on with this program and how that information is being used," Michelle Richardson, legislative counsel for the ACLU's Washington office, said in a telephone interview.
The law isn't "a tool for spying on Americans" and intelligence agencies are required to comply with "an extensive set" of rules, Litt said.
That includes having the secret Foreign Intelligence Surveillance Court review and approve procedures to ensure they comply with the Fourth Amendment, he said.
The national intelligence director, Justice Department and agencies conducting surveillance "regularly and extensively monitor" how the law is being implemented and provide classified reports to Congress, Litt said.
The reports include how many times information about U.S. citizens has been disseminated as part of intelligence reporting, he said.
Reauthorizing the law is the top legislative priority for U.S. intelligence agencies, Litt said. The White House "strongly supports" the House bill, according to a statement of administration policy released yesterday
"I will lose an incredibly valuable source of foreign intelligence information that, I think it's fair to say, has been critical to protecting our country over the last few years," he said.
"I know of specific instances, both involving terrorist attacks and involving other kinds of threats, where we have been able to thwart them or gain significant insight into them as a result of this collection activity."