World number one Ashleigh Barty moved into the semi-finals of the Miami Open with a hard-fought victory over Aryna Sabalenka.

Barty, who won the title the last time the event was played in 2019, rode something of a rollercoaster against her big-hitting opponent in a 6-4 6-7 (5) 6-3 win.

There was nothing to choose between the two in the first set until Sabalenka played a poor service game at 4-4 and threw her racket away in disgust.

Barty saved seven break points across the first two sets and looked poised for victory when she moved 5-4 ahead in the second-set tie-break, with a mini-break, only for Sabalenka to win three points in a row.

The Belarusian let out a huge roar and it was all to play for when they kicked off the deciding set after a 10-minute break in the punishing heat.

But Sabalenka began to feel an abdominal problem midway through the set and Barty pulled away to win, with the victory also guaranteeing she will remain on top of the rankings ahead of Naomi Osaka at the end of the tournament.

The Australian said: “At big points I felt like I was able to produce some of my better stuff and that’s what we’re after. I felt like Aryna did that exceptionally well today, we were both able to serve our way out of trouble at times, so to be able to get a couple of breaks, that was all the match needed really.”

The WTA meanwhile, said in a statement it will encourage its players to accept the coronavirus vaccination when they are offered it after Sabalenka and Elina Svitolina expressed doubts.

Speaking after her previous match, Sabalenka said she did not trust the vaccine and did not want her family to have it while Svitolina said friends had advised her to wait.

The statement read: “The WTA believes in and will encourage everyone to get a vaccine. This will assist in protecting the individual who has received the vaccine, those who have not been vaccinated, and allow our world to move back to the place of normalcy that is desired by all.

“The WTA, with the full assistance from our medical advisors from the Mayo Clinic, have been and will continue to educate our players on the various vaccines, along with the benefits of getting vaccinated.

“This being said, the WTA will not be requiring players to get a vaccine as this is a personal decision, which we respect.”

Svitolina will meet Barty in the semi-finals after the 26-year-old easily accounted for Anastasija Sevastova of Latvia 6-3 6-2 in 69 minutes.

The Ukrainian, ranked fifth, leads the Australian in head-to-head matches 4-1 but lost their last encounter in the final of the 2019 WTA finals.