WASHINGTON – Dogged by fear and confusion about sweeping spy programs, intelligence officials sought to convince House lawmakers in an unusual briefing Tuesday that the government's yearslong collection of phone records and Internet usage is necessary for protecting Americans — and does not trample on their ­privacy rights.

But the country's main civil liberties organization wasn't buying it, filing the most significant lawsuit against the massive phone record collection ­program so far. The American Civil Liberties Union and its New York chapter sued the federal government on Tuesday in New York, asking a court to demand that the Obama administration end the program and purge the records it has ­collected.

The ACLU is claiming ­standing as a customer of Verizon, which was identified last week as the phone company ordered by the government to turn over daily records of calls made by all its customers.

The parade of FBI and intelligence officials who briefed the entire House on Tuesday was the latest attempt to soothe outrage over National Security Agency programs that collect billions of Americans' phone and Internet records.

Several key lawmakers, including House Speaker John Boehner, R-Ohio, refocused the furor Tuesday on the elusive 29-year-old former intelligence contractor who is claiming resp­onsibility for revealing the surveillance programs to two newspapers. Boehner joined others in calling Edward Snowden a "traitor."

But attempts to defend the NSA systems by a leading GOP senator who supports them highlighted how confusingly intricate the programs are — even to the lawmakers who ­follow the issue closely.

Explaining the programs to reporters, Sen. Lindsey Graham, R-S.C., a member of the Senate Armed Services and Judiciary committees, initially described how the NSA uses pattern analysis of millions of phone calls from the United States, even if those numbers have no known connection to terrorism. Director of National Intelligence James Clapper has vigorously maintained that there are strict limits on the programs to prevent intruding on Americans' privacy, and senior officials quickly denied Graham's description.

Graham later said he misspoke and that Clapper was right: The phone records are accessed only if there is a known connection to terrorism.

House lawmakers had more questions and, in many cases, more concerns about the level of surveillance by U.S. intelligence agencies Tuesday after FBI, Justice and other ­intelligence officials briefed them on the two NSA programs.

"Really it's a debate between public safety, how far we go with public safety and protecting us from terrorist attacks ­versus how far we go on the other side," said Rep. C.A. Dutch Ruppersberger of Maryland, the top Democrat on the House Intelligence Committee. "Congress needs to debate this issue."

He said his panel and the Judiciary Committee would examine what has happened and see whether there are recommendations for the future.

Rep. Brad Sherman, D-Calif., like many members, said he was unaware of the scope of the data collection. "I did not know 1 billion records a day were coming under the control of the federal executive branch."