China's top singles player Li Na will be sidelined for at least another three weeks due to a right knee injury, according to a senior Chinese tennis official.

The 25-year-old Li, who had a six-month absence from the WTA Tour last year due to a rib stress fracture, hasn't played since the Antwerp Open in February and her comeback date is still uncertain.

"The knee problem has bothered her for quite a long time, so we decided to keep her off for some time and let her undergo some checks in Germany in early April," China Tennis Association (CTA) vice-director Gao Shenyang said during a promotional event held by national team sponsor TCL recently.

"The injury won't hamper her participation in the Beijing Games in August, but I think we should take it seriously, so the three weeks off will be good for her in terms of her future games, though she is set to lose some ranking points."

The injury-prone star had a sparkling return from her six-month layoff, beating three top-20 players to win her second career title in Australia's Gold Coast in January. She then outclassed world No 6 Anna Chakvetadze and world No 4 Jelena Jankovic to make the semifinals in Antwerp.

But she retired from the Dubai Open and missed the Tier 1 event Pacific Life Open in Indian Wells, and will be sidelined again at the Sony Ericsson Open in Miami next week.

Chinese tennis authorities have repeatedly said that injury prevention will be their main goal ahead of the Olympics in the wake of a number of injuries that forced Li and doubles ace Zheng Jie out for most of last year.

Li is China's favorite to win an Olympic singles medal.

"We will employ overseas trainers and doctors to make sure injuries won't happen again on the national team," Gao said. "Otherwise we will be struggling to reach our Olympic goal in August."

As the team's top sponsor, TCL will organize a series of grassroots events throughout the country next month, including community tennis competitions that are expected to reach 16,000 families in 15 cities, and a tennis Van Jam, which will travel for more than 5,000 km in China in September to promote the sport of tennis.