Whistle-blower AT&T technician Mark Klein says his effort to reveal alleged government surveillance of domestic Internet traffic was blocked not only by U.S. intelligence officials but also by the top editors of the Los Angeles Times.

In his first broadcast interview, as seen tonight on Nightline, Klein describes how he stumbled across "secret NSA rooms" being installed at an AT&T switching center in San Francisco and later heard of similar rooms in at least six other cities, including Atlanta, San Diego, Los Angeles, Palo Alto, San Jose and Seattle. 

"You needed an ordinary key and the code to punch into a key pad on the door, and the only person who had both of those things was the one guy cleared by the NSA," Klein says of the "secret room" at the AT&T center in San Francisco.

Click Here for Brian Ross' Nightline Report on Mark Klein.

The NSA is the National Security Agency, the country's most secretive intelligence agency, charged with intercepting communications overseas.

Klein says he collected 120 pages of technical documents left around the San Francisco office showing how the NSA was installing "splitters" that would allow it to copy both domestic and international Internet traffic moving through AT&T connections with 16 other trunk lines.

"It's gobs and gobs of information going across the Internet," Klein says.

President Bush has acknowledged he authorized the NSA to intercept the communications of people with known links to terrorist organizations "into or out of the United States," but that "we're not trolling through the personal lives of millions of innocent Americans."

Intelligence experts say the NSA has the means to filter out suspect communications with sophisticated machines that spot key words, names, addresses or patterns.

Eventually, Klein says he decided to take his documents to the Los Angeles Times, to blow the whistle on what he calls "an illegal and Orwellian project."

Click Here for Full Blotter Coverage.

But after working for two months with LA Times reporter Joe Menn, Klein says he was told the story had been killed at the request of then-Director of National Intelligence John Negroponte and then-director of the NSA Gen. Michael Hayden.

The Los Angeles Times' decision was made by the paper's editor at the time, Dean Baquet, now the Washington bureau chief of The New York Times.

Baquet confirmed to ABCNews.com he talked with Negroponte and Hayden but says "government pressure played no role in my decision not to run the story."

Baquet says he and managing editor Doug Frantz decided "we did not have a story, that we could not figure out what was going on" based on Klein's highly technical documents.

The reporter, Menn, declined to comment, but Baquet says he knows "Joe disagreed and was very disappointed."

Klein says he then took his AT&T documents to The New York Times, which published its exclusive account last April. 

As the new Washington bureau chief of The New York Times, Baquet now oversees the reporters who have broken most of the major stories involving the government surveillance program, often over objections from the government.

After The New York Times story appeared, Klein filed an affidavit in a lawsuit against AT&T brought by a civil liberties group, Electronic Frontier Foundation.

The NSA says it will not confirm or deny the existence or the purpose of the "secret rooms," but in a filing in the court case against AT&T, Negroponte formally invoked the "state secrets privilege," claiming the lawsuit and the information from Klein and others could "cause exceptionally grave damage to the national security of the United States."

Klein says what he knows won't help terrorists.

"The only people that are being kept in the dark is the American people who are being misled and not realizing, not being told that their private information, that their liberties are being destroyed and tramped on," he said.