NEW YORK (AP) — At first, Tyler Hamilton was impressed with the power Lance Armstrong wielded in cycling circles, his ability to call the head of the international cycling federation at any time — and call him by his first name.

As time passed, Hamilton saw how that power could work against him, too — for example, when he was summoned to the federation's offices and warned he was being monitored shortly after beating Armstrong in a race.

The 41-year-old, who rode with Armstrong on the U.S. Postal Service team from 1998 to 2001, details the years he spent lying about using performance-enhancing drugs and his relationship with Armstrong in his book, "The Secret Race, Inside the Hidden World of the Tour de France: Doping, Cover-Ups and Winning at All Costs."

He said coming clean about secrets he always swore he'd take to the grave gave him a sense of peace after years "of being so stressed out," even well after he retired.

"The truth will set you free, I'd always heard that term," Hamilton told The Associated Press during an interview Wednesday. "Once in a while, when I was younger, I'd lie, then tell the truth and I'd feel better. But this was like a thousand-pound backpack off my shoulders. I was out of cycling, I was continuing to live my life in my post-cycling career. But I was miserable. There was something wrong."

The book, released Wednesday, is a culmination of a gut-wrenching 18 months for Hamilton, who provided details to a grand jury looking into the Armstrong case, then talked about them during an interview on "60 Minutes." All of his information was used in the case the U.S. Anti-Doping Agency brought against Armstrong.

Armstrong has long denied doping but last week chose not to fight drug charges by USADA, which last month erased 14 years of Armstrong's competitive results, including his seven Tour de France titles.

Wearing a light grey suit and long curly hair that brushed his neck, Hamilton looked and sounded much more relaxed than the halting, hesitant person who appeared on "60 Minutes" in May 2011.

"I don't think I was super-comfortable," he said. "I knew I wanted to do it but it was hard getting the words out."

Married last fall for the second time and now living in Montana, Hamilton said the words come much easier now that he's finished the book.

Hamilton's co-author, Daniel Coyle, said he agreed to write the book only if Hamilton gave him full access to his records and files and gave him the chance to independently verify all of Hamilton's recollections.

He said the day Hamilton was called into UCI was "just an interesting portrait of where we were in the sport at the time."

"It was a way to measure the sheer impact," Coyle said. "You could ask, 'Was Lance bigger than the sport?'"

Though many details of the alleged doping that Hamilton writes about were revealed on "60 Minutes," the book also paints a portrait of Armstrong as a power player inside his sport and an intimidating figure, who was not to be crossed.

Hamilton writes about a call he received from the International Cycling Union three hours after a victory over Armstrong, who was no longer his teammate, in Mont Ventoux, France, in the lead up to the 2004 Tour de France. "It felt like being called to the principal's office," Hamilton wrote.

During the 40-minute meeting, UCI officials told Hamilton they'd be watching him closely, but he wrote that the meeting, ultimately, was anticlimactic, "as if the UCI had called me in just to be able to say they called me in."

Hamilton writes that a few days later, Floyd Landis called him and told him the meeting had been engineered by Armstrong but when he confronted Armstrong about it, he denied it.

Landis is the cyclist whose 2006 Tour de France title was stripped. He denied doping for a long time, then admitted he did it and his testimony has also been used in the case against Armstrong.

Armstrong's agent, Bill Stapleton, did not immediately respond to messages seeking comment.

Hamilton said the meeting with UCI sent him an unmistakable message about Armstrong's power. He said he had heard the Texan talking on the phone from time to time in earlier years with former UCI president Hein Verbruggen — a man he and others in the peloton "called Mr. Verbruggen. Lance would call him up and speak to him on a first-name basis."

"I used to think, 'This is good, Lance gets things done,'" Hamilton said. "Then, when I was his competitor and our friendship started to dwindle, that's when I felt the wrath."

Coyle said the day Hamilton was called into UCI was "just an interesting portrait of where we were in the sport at the time."

"It was a way to measure the sheer impact," Coyle said. "You could ask, 'Was Lance bigger than the sport?'"

Hamilton said he told the story because he needed to get it off his chest and wanted to see changes come about in cycling.

"I did what I had to do for myself," Hamilton said. "The best thing I could do was tell the truth. Unfortunately, there were other names involved. He was the biggest name involved. I can't really worry about that. He's a resilient character. He'll be OK. He's one tough dude."