Andy Roddick was forced to dig deep to beat his unfancied opponent in his China Open semi-final Saturday as women's top seed Jelena Jankovic continued her march towards the title.

The big-serving American battled to a 6-2, 6-7 (4-7), 6-1 win against 137-ranked Bjorn Phau while Jankovic staved off a spirited fightback from Vera Zvonareva on the women's side.

Germany's Phau -- ranked 129 places below Roddick -- came into this tournament without a single win on the ATP tour this season but frustrated the second seed with a battling performance.

Roddick hurled his racket to the ground in frustration after losing the second set tie-break but broke Phau's serve three times in the decider.

In the final, Roddick will meet Israel's Dudi Sela, who reached his first ATP final with a 6-3, 6-3 win over seventh seed and Wimbledon semi-finalist Rainer Schuettler.

Sela, who earlier dumped world number five David Ferrer and sixth seed Tommy Robredo from the Beijing tournament, was quickly into his stride, breaking the error-prone Schuettler three times in the opening set.

The 23-year-old kept up his intensity in the second set, forcing what proved to be a decisive break in the sixth game.

He said reaching an ATP final had been a "dream" since breaking into the top 100 of the world rankings.

"Before the match I was very nervous because I wanted to be in the final," he said, adding now he had "nothing to lose."

In the women's draw, Jankovic, last year's losing finalist here, beat Zvonareva 6-4, 2-6, 6-4.

The Serbian world number two took the first set against Zvonareva but powerful hitting from the Russian brought her level.

The players swapped breaks at the beginning of the deciding set but Jankovic forced a further break and sealed the match, which lasted two hours 22 minutes.

"The first set I played quite well and I was dominating but then in the second set I lost my energy and let my opponent come on top of me. She was the one dictating the points," Jankovic said.

"It was not easy. Mentally and physically it was quite hard but at the end I managed to stay calm and finish the match in my favour," she added.

The late evening match in Beijing will feature China's Zheng Jie against Russia's Svetlana Kuznetsova.

In reaching the last four of the women's 600,000-dollar competition, Zheng has matched the best ever performance by a Chinese player here and her run includes victories over world number four Ana Ivanovic and tenth-ranked Agnieszka Radwanska.

Wimbledon semi-finalist Zheng will be looking for a lift from the home fans after she admitted they helped her in her win over Ivanovic, whom she beat on her way to the last four on the grass in London.