MELBOURNE (AFP) - Sixth seed Elina Svitolina dug deep to overcome 17th seeded American Madison Keys in three sets to reach the Australian Open quarter-finals for the second time in a row on Monday (Jan 21).

The 24-year-old Ukrainian won 6-2, 1-6, 6-1 to set up a last-eight clash with either fourth seed Naomi Osaka of Japan or Latvian 13th seed Anastasija Sevastova.

Keys, a US Open finalist in 2017, started slowly but came back to take the second set and put Svitolina under pressure at the start of the third.

The turning point was a marathon 16-minute game early in the deciding set that went to deuce 11 times as Keys chased a decisive break.

But the American's resolve crumbled when Svitolina held off five break points then gained an advantage in the next game.

"I had to put my level up, I'm glad I handled the pressure," said Svitolina, who scored her biggest career win at the WTA Finals in Singapore last October.

"It was very hard because the sun was burning my eyes when I was tossing the ball, so I was very happy to win."

Svitolina was a quarter-finalist at Melbourne Park last year and has made the last eight at Roland Garros twice but is yet to progress further in a Grand Slam.

She has set her sights high this year after her breakthrough in Singapore, targeting a Grand Slam win and world No. 1.

Svitolina pounced as Keys came out of the blocks slowly and raced to a 4-0 lead in the opening set with a double break.

The Ukrainian, who lost her previous two meetings with the American, struggled in the second as Keys stepped up her aggression, coming to the net and adding extra venom to her returns.

The American was rewarded with a double break taking the set 6-1 after 23 minutes.

The early stages of the decider developed into a dogfight before Svitolina prevailed over the frustrated Keys.