PARIS (Reuters) - Serbia's Ana Ivanovic staved off a stirring fightback by compatriot Jelena Jankovic to reach the French Open final with a 6-4 3-6 6-4 victory on Thursday and clinch the world number one ranking.

The second seed, the runner-up last year, led by a set and 3-1 only for Jankovic to level and go ahead 3-1 in the decider herself, before Ivanovic recovered again to set up a final against Russian 13th seed Dinara Safina.

"It was a very tough match - there were lots of ups and downs," a relieved Ivanovic said. "I was just so happy to stay strong in the end and win the match, but it was a very tough one.

"(From 3-1 up in the second set), I think she just started playing really good tennis.

"Maybe I started to be a bit too passive but she's a very good player and if you give her chances, she is going to take them."

Jankovic had been struggling with right arm and right shoulder injuries throughout the tournament but she came out firing as she raced to a 3-0 lead.

Ivanovic, who won just three games in the 2007 final against Justine Henin, looked in trouble again on the big stage but she bounced back superbly, taking the attack to Jankovic to snatch the set and then lead 3-1 in the second.

The second seed had a break point for a 4-1 lead but Jankovic saved it and suddenly the match changed.

As Ivanovic tightened up, Jankovic won seven straight games to lead 2-0 in the decider and though Ivanovic broke back, Jankovic moved ahead again with another break at 4-3.

But Ivanovic, the runner-up at the Australian Open in January, pulled herself together to clinch a victory that ensures she will overtake Russian Maria Sharapova at the top of the rankings when they are released on Monday.

Ivanovic said she expected a difficult final against Safina, who followed up her wins over Sharapova and Elena Dementieva with a straight-sets drubbing of a third Russian, Svetlana Kuznetsova, in the semi-finals on Thursday.

"She has had a great run and it's going to be a very tough match," Ivanovic said. "But I have a day off now, so I just want to recover and hopefully perform well again."

(editing by Justin Palmer)