Australian Open, Melbourne
Venue: Melbourne Park Dates: 17-30 January
Coverage: Watch on BBC TV, Red Button, BBC Sport website (UK only) & Eurosport; listen on BBC 5 live sports extra and online; text commentary online;
Clijsters (right) reached the final in Melbourne seven years ago
Kim Clijsters moved a step closer to back-to-back Grand Slam titles despite a tentative Australian Open quarter-final win over Agnieszka Radwanska.
The Belgian struggled to find her best form but still came through 6-3 7-6 (7-4) against the Polish 12th seed.
Clijsters will face a sterner test against second seed Vera Zvonareva in the semi-finals on Thursday.
Zvonareva cruised into the last four with a comfortable 6-2 6-4 win over a misfiring Petra Kvitova.
The Czech, who previously upset seeds Sam Stosur (5) and Flavia Pennetta (22), struggled at the start as the powerful groundstrokes that had racked up nine successive wins were absent.
A fizzing return down the line in the fifth game threatened to spark the 20-year-old into life and she converted a subsequent break point, but Zvonareva's tidy, if unspectacular, tennis proved enough to secure the opener as she exploited 11 unforced errors from her opponent.
I didn't feel great out there today. I felt heavy in the legs but I hung in there
Two unscheduled interruptions in play, for an illness in the crowd and a distant gun salute to mark Australia Day, allowed Kvitova to gather her thoughts and she briefly threatened to take the contest to a third set.
However, Kvitova's erratic play returned and Zvonareva picked up the final three games to book her place in a third consecutive Grand Slam semi-final.
"She's a very good player," Zvonareva said of her opponent. "She took that opportunity, that little chance that I gave her. She used it and got back into the match.
"But I'm really happy the way I handled the situation after, and I was able to come up with some good shots when I needed it and finish in two sets."
Kvitova said: "I don't think I was nervous but I was little tired. It's 10 matches in a row so it was tough."
Clijsters was a strong favourite to progress against Radwanska, who had been told by a surgeon late last year that she had "1% chance" of playing at the Australian Open after surgery on a stress fracture to her foot in October.
However, five breaks of serve in the first six games suggested the three-time US Open champion was also feeling the nerves as she continues her quest for a first major title away from New York.
Clijsters served out the first set and looked on course when she broke in game seven of the second, but Radwanska battled back and served for the second set, only for Clijsters to convert her fourth break point in an entertaining 10th game.
It came down to a tie-break and Clijsters managed to avoid being drawn into a nervy third set by taking control from 4-4 to seal a Grand Slam semi-final place for the 15th time in her career.
"I didn't feel great out there today," she admitted afterwards. "I felt heavy in the legs but I hung in there, which I needed to because she is a good player."
And looking ahead to facing Zvonareva in the last four, Clijsters added: "I hope my experience can help me but there are some tough players out there. It's going to be tough but they will be two great semis.
"I lost to Vera at Wimbledon last year but then beat her at the US Open. She is playing really well and I am going to have to play better than I did today."