Six-times champion Serena Williams has stormed into the Australian Open semi-finals, extending her run of dominance over Maria Sharapova to 18 matches.

Williams wasn’t always at her best on Tuesday and spoke with the doctor and trainer during a lopsided second set.

But the world No.1 did more than enough to silence Sharapova 6-4 6-1 in one hour and 32 minutes on Rod Laver Arena.

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Williams will step up her bid for a 22nd grand slam title on Thursday, when she faces Agnieszka Radwanska for a place in Saturday’s decider.

Earlier on Tuesday, Polish fourth seed Radwanska defeated Carla Suarez Navarro to seal the first place in the semi-finals of the women’s singles at the Australian Open.

Leading off play on day nine at Melbourne Park, Radwanska breezed through the first set, then was made to work harder before securing a 6-1, 6-3 win on Rod Laver Arena.

Radwanska raced through the first four games before Suarez Navarro got on the board, but the set was quickly over in 28 minutes.

Radwanska’s first-serve percentage of 79 for the set compared to just 54 per cent for her opponent, while Suarez Navarro made 18 unforced errors in a poor display.

In the round of 16, Suarez Navarro lost the first set 6-0 to Australia’s Daria Gavrilova before rallying to win in three sets.

This time around, Radwanska broke to lead 2-0 but this triggered a string of service breaks.

In the sixth game, Suarez Navarro held after six deuces to make it 3-3.

The pivotal moment came when Radwanska broke again to take a 5-3 lead, and after saving a number of break points, she finally sealed victory after an hour and 21 minutes.

– AAP