The Ukrainian world number 29 went to CAS after the International Tennis Federation (ITF) dismissed her appeal against a provisional suspension imposed in January following the discovery of banned substance mesterolone in an out-of-competition sample.

Yastremska, who travelled to Melbourne despite being suspended and was placed into quarantine along with others involved in the tournament, had claimed the positive test was the result of a "contamination event".

The CAS has confirmed her provisional ban will remain in place, ruling her out of the Australian Open, which is scheduled to begin on Monday (February 8).

"Ms. Yastremska therefore remains ineligible to compete, pending the final resolution of her case," the ITF said in a statement.

Yastremska was on one of the three planes to Melbourne where positive COVID-19 cases were later identified, and was among the 72 players forced into a two-week period of strict quarantine prior to the start of the opening Grand Slam of the year.

The Australian Open is scheduled to run from February 8 to 21.

The tournament was postponed by three weeks to allow for the period of quarantine after players arrive in the country.

Calls had been made for the event to be pushed back again due to positive coronavirus tests from players and quarantine periods.

Between 500 and 600 people connected to the Australian Open were today forced into isolation after a worker at one of the tournament's quarantine hotels tested positive, throwing plans for the event into chaos just days before it is set to start.