BERLIN (DPA) - Three-time Olympic swimming champion Sun Yang's hearing in a doping rules matter at the Court of Arbitration for Sport (CAS) will not take place before late October and will be only the second in its history open for the public.

The CAS said Tuesday (Aug 20) that "due to unexpected personal circumstances" involving one party the hearing originally planned for September had to be postponed.

"At the parties' request, the hearing, which will likely take place in Switzerland, will be open to the public (including the media)," CAS said, adding that there has only been one public hearing before, involving swimmer Michelle Smith De Bruin, in 1999.

In the Sun case, the World Anti-Doping Agency (Wada) is appealing a ruling from the swim body Fina which gave Sun a warning over events during a doping test 11 months ago in his native China.

Sun is said to have contested the credential of one drug testing official and a member of his entourage reportedly destroyed a blood test sample.

If Sun, who served a doping-related ban over three months in 2014, is sanctioned by CAS he could miss next year's Olympics in Tokyo.

At the recent world championships in Gwangju, South Korea, where he won two golds, Sun was subject to podium protests by other athletes in connection with the doping issue.