Li Na a step closer to grand slam, but toughest game is yet to come

Li Na carved out another bit of grand slam history for China, then joked she would grab a bag of chips and enjoy watching Serena Williams take on Carla Suarez Navarro. That, though, is unlikely to have been pleasant viewing.

After Li became the first Chinese player to reach the semi-finals at the US Open with a laboured 2½-hour win over 24th seed Ekaterina Makarova, she watched the seemingly unstoppable Williams crush her Spanish opponent 6-0, 6-0, the first "double bagel" in a quarter-final at Flushing Meadows since 1989, when 18-time major winner Martina Navratilova did it to Manuela Maleeva.

Worryingly for Li, who has to stop Williams if she is to reach the final, the American top seed and defending champion insisted her game wasn't peaking and that she had plenty of room for improvement.

Li beat Russia's Makarova 6-4, 6-7 (5-7), 6-2. On three occasions, Li went up a break in the second set, nearing eventual victory each time, but could not finish it off. She was then up 3-0 in the tiebreaker before faltering, but recovered well.

Li has only won one of nine career matches against Williams heading in tomorrow's semi-final.

"Tough, tough opponent," Li said. "But it's a good challenge to play against her."

Li insisted she would try to focus only on herself. Having watched Williams' demolition job, that may prove tricky.