The Court of Arbitration for Sport (CAS) said Monday it has put back its ruling on the two-year doping ban for Maria Sharapova for two months to September, ruling the tennis superstar out of the Rio Olympics.

The 29-year-old Russian tested positive for the banned medication meldonium during January's Australian Open, in a severe blow to her reputation.

If the ban -- which Sharapova has called "unfairly harsh" -- is upheld it would almost certainly end one of sport's most celebrated and high-profile careers.

"Maria Sharapova and the International Tennis Federation (ITF) have agreed to defer the CAS decision until September 2016," said a CAS statement.

"Due to the parties requiring additional time to complete and respond to their respective evidentiary submissions, and several scheduling conflicts, the parties have agreed not to expedite the appeal.

"A decision is expected to be issued by September 19, 2016."

The original ruling was expected by July 18, with Sharapova hoping that a successful appeal would have allowed her to spearhead the Russian tennis team in Rio.

CAS confirmed to AFP that Sharapova will not be able to compete at the Olympics.

Russia's participation at the Games, which begin on August 5, is already under fierce scrutiny after its track and field team was banned for separate state-sponsored doping.

The Russian tennis federation chief said Sharapova's absence in Rio would badly dent their medal hopes.

"(It is) a serious loss for our team at the Olympics as we counted on her medal in women's singles," TASS news agency quoted Shamil Tarpishchev as saying.