Venus and Jankovic to clash in semifinal

(CNN) -- Jelena Jankovic, set to regain the world number one slot next week, defeated Vera Zvonareva in the quarterfinals of Stuttgart's Porshce Grand Prix to book a semifinal with Venus Williams.

Jankovic held her nerve to win 7-6 7-6 as Zvonareva, the Olympic bronze medal winner, produced some dogged resistence.

"That was a hard game, but I am pleased to be in the semifinals," said Jankovic, who will regain the world's top ranking after Serena Williams lost here in the second round.

"It's a great accomplishment to be world number one and I don't know anyone who is not happy about being the best in the world at something. But the competition is still fierce and you have to keep winning."

Jankovic had to work hard for everything in the first set which took exactly an hour and the Serb had to break back the Russian to force the tie-break.

Both players showed their frustration at missed opportunities, but Jankovic found a weakness in Zvonareva's game and used the lob to devastating effect.

The Russian made her frustration work for her by storming into a 2-0 lead early in the second, but Jankovic kept applying the pressure to eventually take the second on a tie-break.

Earlier, Venus Williams admitted the lure of the brand-new sports car on offer for the tournament winner proved the inspiration in her quarterfinal win over Dinara Safina.

Sixth seed Williams needed a little over an hour to beat the third-seeded Russian 6-4, 6-2 and revealed the prize of a Porsche 911 Carrera 4S Cabrio, worth $98,500, is a tempting target as she bids to win Sunday's final. "I love fast cars, I am hoping to win one here and take it for a drive after Sunday," she admitted.

The first set was a tight affair as Olympic silver medalist Safina matched Williams' powerful service game. But the second was a different story as Safina struggled to make any impact as Williams showed her full array of shots to keep the Russian under constant pressure.

In Saturday's other semifinal, Nadia Petrova will meet Belarus teenager Victoria Azarenka. Petrova, the 2006 champion, had a comfortable win over China's Li Na, who knocked out Serena Williams on Wednesday, and claimed a 6-2 6-3 win in just 68 minutes.

"After she beat Serena, I was expecting a hard game and it was a bit easier than I thought it was going to be," said Petrova.

Azarenka trod a much tougher path to the last four as she knocked out Olympic champion Elena Dementieva after a marathon quarterfinal which lasted two hours and 53 minutes.

The 19-year-old Azarenka, who also reached the semifinals of the Berlin Open in May, came out on top after nearly three hours' play to knock out fourth seed Dementieva 7-6 3-6 6-1.

"I just kept fighting," said Azarenka. "She is such a good opponent, I had to fight for every ball, but my legs are pretty dead now."