Lance Armstrong's cycling comeback is in doubt because of a technicality over anti-doping re-entry rules.
Riders coming out of retirement need to be in the International Cycling Union's (UCI) anti-doping programme for six months before being allowed to race.
The sport's governing body said it would make a final decision on this matter later this week.
Its Irish president Pat McQuaid stating: ‘Rules must be respected.’
Armstrong was due to make his comeback to the sport after a three-year hiatus in January’s Tour Down Under.
The issue at the centre of the legal problem is when the six-month countback will begin. The most likely date is August when Armstrong had to return to the USA’s Anti-Doping Agency’s testing programme to take part in August’s Leadville Trail 100 mountain bike race in Colorado.
The team that Armstrong is most likely to ride for on his return is Astana; a team heavily linked to doping in the past. The Kazakhstan-based team was thrown out of the Tour de France in 2007 for doping irregularities from several of its riders.
