* Safina thumps Italy's Pennetta 6-2 6-0
* Will meet Jankovich in final (updates after Jankovic win)
By Simon Cambers
CINCINNATI, Aug 15 (Reuters) - World number one Dinara Safina will take on a rejuvenated Jelena Jankovic in the final of the Cincinnati Open after hugely contrasting wins on Saturday.
Russian Safina stormed into her eighth final of the year with a 6-2 6-0 demolition of Italian Flavia Pennetta, while fifth seed Jankovic saved four match points to beat fourth seed Elena Dementieva 7-6 0-6 7-6 after two hours and 46 minutes.
Safina was at her powerful best as she ended Pennetta's 15-match winning streak in just 55 minutes.
"Every match I have been feeling better," Safina told reporters. "Today, stepping on the court, I was feeling very good and confident."
Pennetta looked a little jaded and Safina was relentless as she broke in the second game and never looked back, reeling off seven in a row to clinch a comprehensive victory.
"I knew I had to be strong at the beginning," said Safina. "When somebody starts to put you under pressure from the first game, it's tough mentally to face it.
"That was the key. I wanted to put the pressure on straight away and to dominate, not let her get into the match."
Pennetta offered no excuses for her defeat.
"Today she was playing much better than me," the 14th seed said. "I was a little bit tired, of course, but I didn't lose because of that.
"In front of me was the number one in the world and she was playing unbelievable."
The real drama, though, occurred under lights as Jankovic and Dementieva fought out a tension-filled semi-final in which both players had match points.
Despite some poor serving -- Dementieva had 17 double faults and Jankovic eight -- the pair produced some of the best tennis of the week, with numerous lung-busting baseline rallies that had the crowd enthralled.
Jankovic snatched the first set on a tiebreak after just one break of serve apiece before Dementieva played a near-flawless second set to level the match.
The third set was an epic in itself as Jankovic held three match points at 5-4, only for the Russian to break back.
The next two games were also breaks before Dementieva forced four match points of her own as she charged ahead 6-2 in the tiebreak.
But Jankovic would not give in and after fighting back to 6-6, Dementieva's 17th double fault gave Jankovic her fourth match point and the Russian netted a forehand to hand her the match.
"I think you saw my reaction -- I was like 'Oh my God, I can't believe I won'," Jankovic said.
"I had three match points and got upset when I didn't win it and then she had I don't know how many match points. I can't believe I won."
The win put Jankovic through to only her second final of the year and the former world number one said she had almost forgotten what it was like.
"It feels unbelievable," she said. "It's been a long time since I was in a final like this. Hopefully I can play well against Dinara, it's going to be tough."
(Editing by Ian Ransom; To query or comment on this story email email@example.com)