"I think it's put a strain on our friendship," Pettitte said in an eagerly awaited news conference Monday at the New York Yankees' spring training complex.
Pettitte apologized to the Yankees, Houston Astros and his fans for the "embarrassment" he caused them by taking HGH.
Pettitte arrived at spring training earlier in the day and threw a bullpen session at the minor league complex. Later, he met reporters for about an hour.
"I never want a young person to do what I did," Pettitte said. "I'm sorry for the mistakes I have made."
Pettitte sat alone at a podium, taking dozens of questions. He often paused to collect his thoughts and several times patiently asked reporters "did I answer your question?"
It had been about a month since he had spoken to Clemens, Pettitte said.
"I can't even describe how uncomfortable a situation" this has been.
With Yankees teammates Derek Jeter, Mariano Rivera and Jorge Posada in attendance, along with two of his lawyers, Pettitte acknowledged he had considered not playing because of the ongoing situation.
"That wouldn't be the thing to do as a man. I felt like I needed to come out and face you guys and whatever circumstances that come I'll take it, I'll take it like a man and I'll try to do my job," he said.
Pettitte was excused from testifying publicly at a congressional hearing last week after he gave a deposition and an affidavit. In addition to his December admission that he used HGH for two days in 2002 while with the Yankees, he said he injected himself with HGH for one day in 2004 while with the Astros after obtaining two syringes from his father.
"I was never going to bring my dad up," he said.
Pettitte said there were no other times he used performance-enhancing drugs. "There are no other surprises out there," he said.
The 35-year-old lefty with 201 regular-season wins and four World Series championship rings said he did not feel as if his accomplishments were tainted.
"All I can tell you, from the bottom of my heart I know why I did this. I did it because I was told it might be able to help me," he said. "If people think I'm lying, then they should call me a cheater.
"Do I think I'm a cheater? No, I don't," he said. "Was it stupid? Yes, I was stupid. Was I desperate? Yes, I probably was."
Pettitte said in his previous statement that Clemens had discussed nearly a decade ago using HGH. In addition, Pettitte testified Brian McNamee, the former personal trainer for Clemens and Pettitte, had spoken in 2003 or 2004 about steroids use by Clemens.
Clemens claims Pettitte "misremembers."
"I think Roger knows how I feel about him. He knows I've admired him and continue to admire him. He's a great friend to me," he said.
Pettitte said he did not watch the Congressional hearings last week in which Clemens and McNamee testified. Pettitte professed his friendship for both men and said he hoped to remain on good terms with both of them.
"This has been a horrible situation for me," he said. "I'm hoping and praying I don't have to do anything else with this."
Pettitte does not appear to be at risk of a suspension for his admissions. HGH was not banned by players and owners until January 2005.
"If it was illegal in baseball, I wouldn't have done it," he said.
However, Pettitte could remain ensnared between McNamee and Clemens, who denies allegations that he used performance-enhancing drugs. Dealing with his first controversy since he was hired to replace Joe Torre, manager Joe Girardi said it was too soon to tell whether the matter will end soon for Pettitte.
"I think a lot of that depends on what happens with Roger and what he continues to do. If that was to all die down, I think it would pretty much go away," Girardi said Sunday. "But, obviously, there's some litigation there that Andy might be a part of, so from that standpoint, it could linger."
Clemens has filed a civil suit against McNamee claiming defamation, and there could be a criminal investigation of the conflicting accounts given before Congress by Clemens and McNamee.
Girardi understands any additional admissions of drug use by Pettitte "would become a huge story."
"But my thought is Andy has probably told everything that there is," Girardi said.
During the season, spectators on the road are likely to remind Pettitte of HGH use.
"You know how the fans are. They're going to say anything to distract the pitcher," Rivera said. "Hopefully, it's not too bad, because it always happens."
Pettitte was 15-9 with a 4.05 ERA last year in his first season back with New York following three years on the Astros. He announced Dec. 3 that he would accept the Yankees' $16 million standing offer to return for another year.