Published: May 20, 2010 12:11 PM EDT
Updated: May 20, 2010 12:10 PM EDT

NEW YORK (AP) - The Wall Street Journal is reporting that disgraced American cyclist Floyd Landis has admitted to systematic use of performance-enhancing drugs, and accused seven-time Tour de France champion Lance Armstrong of involvement in doping.

The paper says Landis, who was stripped of his 2006 Tour de France title for doping, sent a series of e-mails to cycling officials and sponsors detailing his use of banned drugs. Landis also admitted to doping in an interview with ESPN.com. Pat McQuaid, the head of cycling's world governing body UCI, questions Landis' credibility.

McQuaid tells The Associated Press that Landis is "seeking revenge" and holds a "grudge" against Armstrong and others. McQuaid says Armstrong has been accused of doping many times, but nothing has ever been proven.