China's star swimmer Sun Yang, who is fighting to save his career after a doping controversy, has been given new hope of competing at the Olympics after China said reigning world champions were eligible for Tokyo.

The China Swimming Association's announcement came as the three-time Olympic champion prepares for a new tribunal hearing over his refusal to give a doping sample when testers visited his home in September 2018.

Sun, the 1 500m world-record holder, won the 200m and 400m at the 2019 world championships in South Korea, where he faced protests on the podium from fellow swimmers over his doping record.

The China Swimming Association laid out its eligibility requirements for the Olympics on Thursday, saying all gold medallists at the 2019 world championships can participate.

The 29-year-old is not taking part in this week's Chinese championships and Olympic qualifiers in Quingdao, according to Chinese media.

Sun was suspended for the maximum eight years by the Court of Arbitration for Sport in February last year refusing to give samples during a surprise doping test where a vial of his blood was smashed with a hammer.

But Switzerland's top court overturned the ban in December, in a surprise decision in which it said CAS was guilty of bias.

Sun will reappear before the sports tribunal from 24-28 May, just two months before the Tokyo Olympics.

Sun has fiercely protested his innocence in the testing affair, claiming the inspectors did not produce documents proving their identities.

It was not Sun's first doping controversy: he was suspended for three months in 2014 after testing positive for the stimulant trimetazidine, in a case that was only made public after he had served most of the sentence.

Source: News24