China's Li Na concedes her serve needs more work if she is to achieve her goal of breaking into the world's top five after losing in the Australian Open semifinals yesterday.

The 16th seed was speaking after going down to defending champion Serena Williams 7-6 (4), 7-6 (1) in a two-hour thriller at Rod Laver Arena.

Williams blasted down 12 aces in the match against Li's one, one of those coming on set point in the first set and another on match point.

"I think that I have to practise my serve much, much more," said the 27-year-old from Wuhan, whose run to her first Grand Slam semifinal is expected to see move into the top 10 when new rankings are released.

She is currently world No 17.

"I mean, I had break point (at 3-3 in the second set) but she just served an ace. I had deuce and she also served an ace.

"It makes the game easy for her to play - if she wants to win the point, she just serves an ace.

"So after the match I was talking to my team, talking to the coach and I told them we have to work a lot on the serve."

Li did not serve badly in the match and only allowed Williams four break points in the long second set, none of which the American converted.

But she was unable to use her serve as a weapon in the same way as her opponent.

Nevertheless, Li was not downcast, saying she had played well and improved her game over the past fortnight.

"I lost the match, of course I was a little bit sad that it stopped in the semifinal," she said. "But it was a good day for my tennis. I played well today."

Li and countrywoman Zheng Jie have captured considerable attention this week with their record-breaking runs to the semifinals.

No two Chinese players had ever got that far before.

But Li had a word of warning for anyone who believed it was only the women who were ready to give the established order a shake.

"There are many, many men players in China," she said. "They're still asleep, they haven't woken up."