Serena Williams has claimed that she expects a tough contest against Agnieszka Radwanska when they meet in the Wimbledon ladies' singles final on Saturday.

Williams booked her place in a seventh final at SW19 with a straight-sets victory over Victoria Azarenka, while Radwanska ended Angelique Kerber's tournament also in straight sets.

"She's unbelievable," the American said of Radwanska. "She's playing great, she's going to get every ball back."

Williams hit 25 aces during her semi-final on Centre Court, beating the previous ladies' singles record which she had set by one.