MARIA Sharapova remained on course for a third grasscourt title at Edgbaston after the former Wimbledon champion moved into the semi-finals of the AEGON Classic.

Sharapova started well against Belgian opponent Yanina Wickmayer but was forced to work hard over three sets for a 6-1 2-6 6-3 win.

The Russian, unseeded in the tournament after plunging down the rankings due to an injury lay-off, hammered down seven aces as she produced a series of strong service games in a match which stretched to one hour and 45 minutes.

‘‘I thought I started off really well and the tennis was at a pretty high level,’’ Sharapova, the winner in 2004 and 2005, said.

‘‘But I started slowing down in the second set and let her get back in the match.

‘‘We’ve always had pretty difficult encounters and I just played her last week at the French Open and it was three tough sets, but that was on clay, and this is a new tournament and a different surface.’’ Sharapova will face China’s Na Li in the last four today, after the latter progressed with a straight-sets victory over Stefanie Voegele.

The fourth seed, the highest- ranked player in the last eight, comfortably won the first set 6-3 but was forced to a tie-break in the second by the Swiss, coming out with a 7-6 (7/3) win.

The other semi-final will be contested between India’s Sania Mirza, who ousted Melinda Czink 6-1 7-6 (7/4), and Slovakian Magdalena Rybarikova, who bettered Urszula Radwanska in straight sets to win 6-3 6-3.