TOKYO (AFP) - Malaysian badminton superstar Lee Chong Wei and China's Olympic champion Li Xuerui roared to the men's and women's finals at the Japan Open on Saturday, living up to their world No. 1 billings.

Lee tamed Japan's Kenichi Tago 21-15, 21-17 in the men's semi-finals, gearing up for a fifth Japan Open title.

Li, competing in her first Japan Open, struggled in the second game but outlasted Asian champion Sung Ji Hyun of South Korea 21-15, 23-21 in the women's penultimate round.

Lee faces Hong Kong veteran Hu Yun in the men's final on Sunday. Hu outlasted Denmark's European champion Jan Jorgensen 21-13, 19-21, 21-15.

Li's final opponent is Chinese Taipei's Tai Tzu-ying, ranked seventh in the world, who put down Chinese player Liu Xin 15-21, 21-19, 21-9.

The 31-year-old Lee - who has already won three events in the top-flight World Superseries this year in Malaysia, England and India - led the first game from the outset against Tago, 24, whom he beat in the Japan Open final last year.

After his lead was narrowed from 17-11 to 18-15, the two-time Olympic silver medallist scored three straight points.

In the second game, Lee kept the lead as wide as seven points after 3-all. After 19-17, he smashed a shot in and sent another rolling over the top of the net to win the match.

"Too strong," Tago, the world No. 4, shouted at Lee as the Malaysian was talking to reporters after stretching his head-to-head record against the Japanese to 17 wins and one loss.

When Japan beat Malaysia 3-2 in the Thomas Cup men's team championship final in New Delhi three weeks ago, Lee whipped Tago in straight games.

"I have not tuned up well since the Thomas Cup and my condition is not so good," Lee said. "But I want to win every match in front of me. I wish to improve myself step by step and peak for the 2016 Rio Olympics."

The women's top seed, Li, blamed loss of concentration for her struggle in the second game against Sung, whom she has defeated in all their six previous encounters.

"I played as usual today but I relaxed myself somewhat toward the end of the second game to let my opponent battle back. It was a bit dangerous," the 23-year-old said.

Li, who won the Superseries final last year, has taken the Malaysia Open but finished runner-up in three more Superseries events to Chinese team-mates so far this year.

Asked about her final opponent Tai, 20, whom she has beaten in all their seven encounters, she said: "I am confident to some extent. But what's past is past. Tomorrow is tomorrow. I must study about my opponent and be prepared."

Hu, 32, seeded eighth, said he did not pressure himself to beat Denmark's Jorgensen, who has the 2013 French Open and the 2010 and 2011 Denmark Open titles to his credit.

"I think my opponent made mistakes as he became too desperate to win as our score got so close towards the end," he said.

"As I did not expect to win, I feel happy," Hu said. "I felt tense. But I could put a smile on my face while I played because I thought I won't regret if I lose."