Elina Svitolina is safely through to the Australian Open quarter-finals after a see-saw battle with American Madison Keys.

The Ukrainian sixth seed overcame blisters and a second-set hiccup to take out the fourth-round match 6-2 1-6 6-1 on Margaret Court Arena.

A marathon 16-minute third game in the final set proved decisive with Svitolina surviving five break points before holding her serve and then running away with the win.

It keeps alive her hopes of supplanting Simona Halep as the world No.1.

Svitolina has never progressed further than the quarter-finals of a grand slam and the result mirrors last year’s final eight showing at Melbourne Park, when she lost to Belgian Elise Mertens.

After winning the WTA Finals in Singapore late last year, the 24-year-old looks poised to take the next step.

A former world No.3, Svitolina hadn’t beaten Keys in their previous two clashes, including their 2017 US Open quarter-final meeting.

Storming through the second set it appeared Keys had all the momentum but that shifted when Svitolina somehow held firm when serving at 1-1.

The game was almost as long as the entire second set with Keys crumbling after she failed to take advantage of the numerous break-point chances.

Svitolina will play US Open champion Naomi Osaka or 2018 US Open semi-finalist Anastasija Sevastova for a place in the semi-finals.