(CNN) -- Cyclist Floyd Landis has acknowledged using performance-enhancing drugs for most of his career after disputing for years a positive doping test result that led to his suspension from the sport, two news organizations reported on Thursday.
Landis also sent e-mails saying that other cyclists have used performance-enhancing drugs, including Lance Armstrong, the American seven-time Tour de France winner, one of the news outlets reported.
Armstrong has repeatedly denied taking such drugs. Before a Tour of California stage race on Thursday -- where he later crashed, prompting a trip to a hospital -- he told reporters: "We have nothing to hide. We have nothing to run from," and said Landis has been threatening him and others for years.
ESPN.com reported that Landis said in an interview that he consistently used the red blood cell booster erythropoietin, commonly known as EPO, along with testosterone and the human growth hormone and that he received frequent blood transfusions.
He also used female hormones and, once, insulin, ESPN.com reported. He is coming forward now because years of deceit have taken a toll on him, the site quoted him as saying.
Pat McQuaid, president of the International Cycling Union, told CNN on Thursday he was "very annoyed and very angry" after hearing of Landis' revelations.
"It just seems to be one last roll of the dice from a very desperate man," McQuaid said.
Landis sent e-mails to cycling and anti-doping officials recently that implicate dozens of other athletes in such activities, ESPN.com and The Wall Street Journal reported.
The Wall Street Journal reported it had seen three of the e-mails, dated between April 30 and May 6, and that officials with USA Cycling and the International Cycling Union were copied on them.
Three people who have seen the e-mails and spoken with Landis about them confirmed their authenticity, according to The Wall Street Journal.
The Journal said Armstrong was among those implicated in the e-mails. But Armstrong said on Thursday, "I would say that I'm a little surprised, but I'm not. In all honesty, this has been going on for a long time."
He said Landis began harassing him a few years ago. "At that time, we largely ignored him ... finally, a year or so ago, I told him, 'Listen, do what you have to do. We have nothing to say.' "
Landis began threatening him and others about a month ago, right before the Tour of California began, Armstrong said.
He added that Landis' specific claims regarding him are "not even worth getting into. I'm not going to waste your time or my time. I think history speaks for itself here."
Asked about Landis pointing the finger at him, Armstrong said, "He pinpointed a lot of people. Let's be honest, I mean, my name will be at the top of the story. My name will be in the headline. But at the end of the day, he pointed the finger at everybody still involved in cycling, everybody that's still enjoying the sport, everybody that still believes in the sport, everybody that's still working in the sport was in the crosshairs."
McQuaid said he had seen copies of e-mails sent to U.S. cycling officials, but would not divulge their contents. "Basically, it's largely along the same accusations that have appeared in the media today," he said.
"Here we have a guy who, you know, for the past four years, has stood in front of a couple of courts in proceedings and denied taking any doping products, denied even seeing evidence of doping activities," McQuaid said, adding that Landis wrote a book saying "authorities were against him" and set up a Web site so fans could help fund his fight to discredit the positive testing result, only to turn around later and acknowledge doping.
"To some extent, you have to question his credibility," McQuaid said.
"This is a man that's been under oath several times and had a very different version," Armstrong said. "This is a man that wrote a book for profit and had a completely different version. This is somebody that took, some would say, close to a million dollars from innocent people for his defense under a different premise, and now that it's all run out, the story changes."
But he said he didn't want to mount a personal attack on Landis. "I don't think he's a good guy or a bad guy," Armstrong said. "I think he certainly has some issues."
Landis spent as much as $90,000 a year on performance-enhancing drugs and consultants to help him build a training regime, ESPN.com reported.
However, he still maintains that the 2006 positive test result for synthetic testosterone at the Tour de France was inaccurate, saying he did not use synthetic testosterone that season, although he did use human growth hormone during that time, ESPN.com reported.
"There must be some other explanation, whether it was done wrong or I don't know what," Landis said, according to ESPN.com.
"The problem I have with even bothering to argue it is [that] I have used testosterone in the past and I have used it in other Tours, and it's going to sound kind of foolish to say I didn't."
He told the Web site he has spent an estimated $2 million battling the test result, which caused him to be stripped of his 2006 Tour de France win and to be suspended from cycling for two years.
He told ESPN.com that if he could pay his donors back, he would, but he said he does not have the money.
The Wall Street Journal reported that in an April 30 e-mail to Stephen Johnson, president of USA Cycling, Landis said that one of Armstrong's longtime coaches introduced Landis to using steroid patches, blood doping and human growth hormone in 2002 and 2003, during Landis' first two years on the U.S. Postal Service team.
Armstrong helped him understand the way the drugs worked, Landis wrote, according to The Wall Street Journal.
"He and I had lengthy discussions about it on our training rides, during which time he also explained to me the evolution of EPO testing and how transfusions were now necessary due to the inconvenience of the new test," the Journal quoted the e-mail as saying.
In a statement, USA Cycling reiterated its zero-tolerance stance on doping. "In accordance with the World Anti-Doping Agency's Code of Athlete's Rights, USA Cycling does not and will not discuss doping allegations, investigations or any aspect of an adjudication process," Johnson said in the statement.
"There are many accusations being circulated and we are confident these will be thoroughly investigated by the appropriate authorities."
Landis wrote that Armstrong's coach taught him to use synthetic EPO and steroids and how to carry out blood transfusions that doping officials wouldn't be able to detect, the Wall Street Journal said.
He said that after breaking his hip in 2003, he flew to Spain and had two half-liter units of blood taken from his body in three-week intervals to be used during the Tour de France.
The extractions took place in Armstrong's apartment, Landis wrote, and blood bags belonging to Armstrong and a teammate were kept in a refrigerator in Armstrong's closet, the Wall Street Journal said.
Landis said he was asked to check the temperature of the blood daily, and when Armstrong left for a few weeks, he asked Landis to make sure the electricity didn't go off and ruin the blood, the newspaper said.
Armstrong said that besides being false, the timeline and other details in the e-mails were off.
Landis told ESPN.com that he realizes his credibility is questionable and that he has no documentation for many of the claims he is making about other riders or officials and it is his word against theirs.
"I want to clear my conscience," Landis told the Web site. "I don't want to be part of the problem anymore. With the benefit of hindsight and a somewhat different perspective, I made some misjudgments.
"And of course, I can sit here and say all day long, 'If I could do it again I'd do something different,' but I just don't have that choice."
Armstrong said on Thursday, "For somebody that says, 'I'm here to clear my conscience,' then why are you sending e-mails to people's sponsors, other people's partners, to the organizers of a race, to the sponsors of a race? That has nothing to do with your conscience."
He said he had no plans to take legal action against Landis. "Legal action takes time, takes energy, takes a lot of money. I have sued a few people in my day and been successful there ... I don't need to do that anymore. My energy needs to be devoted to the team, to Livestrong, to my kids. I'm not going to waste my time."
ESPN.com also quoted Landis as saying, "I don't feel guilty at all about having doped. I did what I did because that's what we [cyclists] did and it was a choice I had to make after 10 years or 12 years of hard work to get there; and that was a decision I had to make to make the next step. My choices were, do it and see if I can win, or don't do it ... and I decided to do it."
He told ESPN.com he never felt forced or threatened to use performance-enhancing drugs. He said his first use was in June 2002, when he was a member of the U.S. Postal Service team. He said the fact that the World Doping Agency's statute of limitations for doping offenses is eight years factored into his motivation for coming forward.
He said he has saved his records, journals and diaries and has offered, in meetings with U.S. anti-doping authorities, to share them, ESPN.com said.
"Landis has been banned by the sport he's been caught doping and banned from the sport in the past," McQuaid said. "And that's correct, and that's the way it should be."
Cycling, he said, has "moved on a good bit" and is in "a much healthier state today."
In a statement on its Web site, the International Cycling Union said it "regrets that Landis has publicly accused individuals without allowing sufficient time for the relevant U.S. authorities to investigate."
Asked whether there should be an in-depth investigation, McQuaid said no, adding "we've had enough inquiries into individual doping cases ... This seems to be an agenda of one individual who is, to my mind, a very sad case."
In the e-mails, Landis wrote that current anti-doping efforts are "a charade," The Wall Street Journal said.
He also detailed how to use EPO and avoid detection and said he helped other teammates take the substance before a Tour of California race, the newspaper said.
A trying day for Armstrong was to end in more disappointment after he was forced to abandon the fifth stage of the Tour of California after crashing.
Armstrong and Jose Luis "Chechu" Rubiera, a teammate on the Radio Shack squad, crashed during the Amgen Tour of California stage race, said team director Johan Bruyneel. He said on his Twitter account that the riders were involved in "a huge crash" and Armstrong had been taken to a hospital for X-rays.
A photograph Armstrong posted on his Twitter page late Thursday afternoon shows a sutured gash underneath the outside corner of his left eye. Armstrong is sitting in a vehicle and looking at the camera with a serious expression.
"Just when I thought I couldn't get any uglier," the caption reads.
Several other riders from other teams also were involved in the crash.
Photographs taken after the crash show a race official tending to the bloody cut under Armstrong's left eye. The athlete was standing and did not appear to be in any great distress.