Delighted Clijsters surprised by progress

Former champion Kim Clijsters admitted she was surprised to have reached the US Open semi-finals soon after coming out of a two-and-a-half-year retirement.

Playing on a wild card in just her third tournament since coming out of retirement having become a mother for the first time, Clijsters breezed past China's 18th seed Li Na in just 63 minutes, winning 6-2 6-4 to set up a mouth-watering last-four clash with defending champion Serena Williams.

The victory was the 26-year-old Belgian's 100th career grand slam win in her first US Open since winning it in 2005 and she said: "I never had the mentality before the tournament that I would get to a semi-final or final at the grand slams."

She added: "I definitely didn't have that idea but something switched with me after Toronto (her second tournament back) where I felt like 'Okay, I can compete with these girls', because that was obviously a big question in my mind."

Williams beat Italy's Flavia Pennetta 6-4 6-3 in their quarter-final on Tuesday night.

The defending champion's serve played a significant part in her victory as she hit seven aces and finished with an 86% first serve success.

The American is now relishing a showdown with the returning Clijsters.

Williams said: "She is such a great person and I only wish the best for her - though not in the next match of course.

"It will be a great match. She has nothing to lose and is having so much fun, which makes me so happy."