Phelps hints at 'possible Olympic comeback' by rejoining drug-testing programme

US Olympic swimmer Michael Phelps has rejoined his country's drug-testing programme in the strongest sign yet that he could return for the 2016 Rio de Janeiro Olympics.

According to Stuff.co.nz, the US Anti-Doping Agency said that Phelps was among the athletes who underwent doping tests in the third quarter, the period ending Sept. 30, adding that he was tested twice.

By subjecting himself to drug testing, Phelps sets himself up to begin competing again by next summer if he chooses, the report said.

FINA requires an athlete to be tested for at least nine months before taking part in sanctioned events, the report added.

Last month, coach Bowman said that Phelps was occasionally training with the group to get back in shape.

Phelps will be 31 at the time of the opening ceremony for the Rio Games, not that old, really, for today's top-flight swimmers, who have more opportunities to cash in on their success and can extend their athletic careers well into their 30s, according to the report.