PARIS - Sentimental favorite Roger Federer did not quite follow the script yesterday in the French Open. He decided to go for high drama.

Striving to complete a career Grand Slam, the Swiss star came from behind twice in the semifinals to beat big-serving Juan Martin del Potro of Argentina, 3-6, 7-6 (2), 2-6, 6-1, 6-4.

Playing in his fourth consecutive Roland Garros final, Federer will try for his 14th major title to match Pete Sampras' record.

"There's still one more step," Federer said. "I was a bit lucky, but I fought well. Juan Martin was playing really well."

Federer's opponent tomorrow will be No. 23-seeded Robin Soderling of Sweden, who extended his improbable Roland Garros run by beating No. 12 Fernando Gonzalez of Chile in another seesaw semifinal, 6-3, 7-5, 5-7, 4-6, 6-4.

With nemesis Rafael Nadal eliminated in the fourth round, Federer faces a less daunting path to that elusive Roland Garros championship. He is 9-0 against Soderling.

But then Federer had swept his previous five matches and 12 sets against del Potro, who was the No. 5 seed. The 6-foot-6 Argentine rose to the occasion in his first major semifinal and kept on the offensive for much of the match, but began to tire in the fourth set.

Federer broke for the first time 21/2 hours into the match to lead, 3-1. Del Potro lost his next two service games as well, allowing Federer to sweep seven games in a row and finally take the lead.

By then, Federer was in top form, gliding across the clay that has vexed him in the past. The No. 2 seed won a frantic rally and a standing ovation by lunging to slice a forehand into the open court for a 3-1 lead in the fifth set. There were more highlight-reel shots down the stretch.

Del Potro greeted him at the net with a handshake and a smile.

"I just congratulated him and wished him good luck," del Potro said. "I said everybody wants him to lift the trophy at the end."

In the all-Russian women's final today, top-ranked Dinara Safina will try for her first Grand Slam title against Svetlana Kuznetsova, the No. 7 seed.

Federer trailed for much of the semifinal, struggling to hold serve and unable to break. Sensing his once-a-year opportunity again slipping away, he slapped himself in the face after losing one frantic rally.

Maybe that helped. And maybe he was buoyed by a crowd that kept chanting "Ro-ger! Ro-ger."

Del Potro made one last charge in the final set, hitting several ferocious shots to break for 3-all. But he missed all eight first serves in the next game and finally dumped a weary second serve into the net on break point.

"I feel so sad," del Potro said. "I really wanted to be in that final, and now I'm going to have to watch it on TV."

On a cool, cloudy, evening, Federer looked out of sorts early, failing to convert two early break points and losing serve at 2-all. He twice fell behind, love-40, while serving and shanked an easy overhead, perhaps a sign of nerves.

Next up: Soderling. He scrambled the draw with his win Sunday over the four-time defending champion. Federer has been beaten in the French Open each of the last four years by Nadal, the last three times in the final.