China's Zhang Yining ruthlessly dispatched old schoolmate Li Jia Wei, now of Singapore, in the women's Olympic table tennis semi-final on Friday after a rivalry which dates back to when they were five-year-olds.

Zhang's 9-11, 11-8, 12-10, 11-8, 11-5 win guaranteed that China would maintain its stranglehold on the women's table tennis gold, having won every one since the sport debuted at the Olympics [Images] two decades ago.

She will meet compatriot Wang Nan in the final.

World number one Zhang and Li, the highest-ranked non-Chinese player, trained under the same Beijing [Images] coaches until Li was recruited to play for Singapore at the age of 14.

They neatly mirrored each other in their attacking topspin styles, going toe-to-toe in long rallies.

"We're really familiar, we really understand each other, even our personalities," Zhang said.

After an uncharacteristically rigid start to the match, Zhang showed her ruthless streak, repeatedly driving the ball in tight to Li's body.

"I've had little contact with her since she went to Singapore, so I don't feel conflicted (playing) against her," Zhang said.

Li, now 27, was reluctant to offer much in the way of praise.

"I don't think her shots are that difficult to handle," the Singaporean said. "I just didn't take advantage of my opportunities."

In the other semi-final, Wang Nan, the "big sister" of Chinese table tennis at the age of 29, taught the up-and-coming Guo Yue a lesson in poise.

"I controlled the match overall. She also played well but from the fifth game on, she seemed to lose her calm," Wang said. "Time. She just needs time and she'll improve."

Wang lost two games with lopsided scorelines but never looked rattled. She won the match 3-11, 11-8, 4-11, 11-7 11-3, 11-6.