The report said the American's e-mails detailed his systematic use of the drugs during his career.
"I want to clear my conscience," the 34-year-old told ESPN. "I don't want to be part of the problem any more."
"Now we've come to the point where the statute of limitations on the things I know is going to run out or start to run out next month. If I don't say something now then it's pointless to ever say it," he said.
The Wall Street Journal said it had reviewed three emails sent earlier this year.
"Mr Landis copied seven people on these three e-mails, including officials with USA Cycling and the International Cycling Union (UCI)," the report said.
"Three people who have seen the emails and spoken to Mr Landis about them say they are authentic."
