The world champion, world number one and hot favorite won 11-4, 8-11, 11-4, 11-9 and 11-6 against his childhood good friend, No. 11 seed.

Zhang, appearing relaxed, said he felt less pressured than two days ago. "I feel much better now. The pressure was huge two days ago. Jiang and I are very familiar with each other. So I feel more comfortable today."

Zhang narrowly made into the quarterfinals on Monday, after being dragged into a tight seven-set match by five-time Olympian Vladimir Samsonov of Belarus.

Asked why his coach Liu Guoliang touched his ears at the break after the fourth set, Zhang said Liu told him to relax. "He said I already led Jiang 3-1, and there this no need to play so cautiously."

Jiang, who moved to Hong Kong from the Chinese mainland in 2005, said he trained together with Zhang Jike in east China's Shandong Province since they were 11. And they both later entered the national youth team. "We were good friends and know each other's playing style very well."

Jiang said it was pity that he didn't take the chance and win the fourth set when he was at 9-9 with Zhang. "I think any player competing against China would feel pressured in the clutch moment. But generally I think I played well."

Zhang will face Germany's Dimitrij Ovtcharov in the semifinals on Thursday. Ovtcharov entered the top four after a seven-set tight match against Denmark's Michael Maze on Tuesday.

Talking about Zhang's nervous start to the tournament, coach Liu said it's because Zhang has a target in his mind (a gold medal). "I have talked to him about this. He must forget that he is world number one in order to fully realize his potential."

Liu said opponents in the semifinals are very tough. "The most important thing to us is to let go all the pressure and really go for it. We are prepared for hard battles. But we are confident that we will win."

Zhang's teammate Wang Hao, seeded No. 2, comfortably booked a seat in the semifinal after beating Seiya Kishikawa in four straight sets (11-4, 11-5, 11-3, 11-5), dashing Japan's last hope of claiming an Olympic medal in table tennis singles events in London.

Wang, twice Olympic silver medalist, said he had prepared for a hard game against Kishikawa but it turned out all right.

Wang will face Chuang Chih-Yuan of Chinese Taipei, No. 5 seed, in the semifinal. Chuang entered the semifinal after beating Romania's Adrian Crisan 4-0.