TENNIS/Australian Open Championships:Ana Ivanovic admitted preparation was the key to her first career victory over Venus Williams which took her into the semi-finals of the Australian Open.

World number three Ivanovic, who became the second of three Serbs into the semi-finals at Melbourne Park alongside Jelena Jankovic and Novak Djokovic in the men's singles, completed a 7-6 (7/3) 6-4 victory to avenge four previous defeats at the hands of the American.

The 20-year-old will now face Daniela Hantuchova, who defeated Polish 29th seed Agnieszka Radwanska on the Rod Laver Arena.

"I worked very hard in my off-season," said Ivanovic, who joined forces with Australian strength and conditioning coach Scott Byrnes prior to Wimbledon in 2006.

"I did a lot of stair sprints, sprints up the hills, in a gym, and also a lot of footwork on the court, tennis-specific footwork.

"I'm really happy to see the results because there were moments I was struggling, of course, because it's important to realise that it has to be hard on your practice court so it will be easier for you in your matches."

In a first set that featured six breaks of serve in the opening seven games, Ivanovic jumped into an early 2-0 lead before Williams hit back.

A crunching forehand off the Williams serve set up three break points for the Serbian, which she secured when the eighth seed hit a return into the net.

Williams, playing with her thigh heavily strapped, fought back to make it 3-2, and neither player could subsequently hold serve until Williams did so for the first time to level the encounter at 4-4.

The set headed to a tie-break and Ivanovic took control after reeling off five consecutive points, before taking the upper hand in the match when Williams hammered a simple-looking backhand volley into the net.

Williams broke her opponent early in the second set to take a 2-0 lead but Ivanovic broke back on the way to levelling at 3-3. After slipping to 15-40, Ivanovic battled back and claimed victory when the American hit a forehand well wide.

Afterwards, Ivanovic admitted the victory was particularly sweet against an opponent who had proved so challenging in previous meetings.

"I was looking for some revenge," she said. "I went out there and from the first moment on I tried to think only on each point. I thought I played some good tennis."

Williams insists she can still be a force despite not reaching the semi-finals at Melbourne Park for the fifth year in a row.

"I have full expectations and aspirations to continue to play high-quality tennis and to continue to be a champion", she said.

Slovakian number nine seed Hantuchova believes a stronger mindset helped propel her into her maiden grand slam semi-final. Five years after advancing to her last grand slam quarter-final, Hantuchova took the belated next step when she beat Radwanska 6-2 6-2.

The other semi-final is between Jelena Jankovic and Maria Sharapova.