Serena Williams has reached the semi-finals of the US Open thanks to a 6-3 6-2 victory over Flavia Pennetta in New York.
The defending champion made the worst possible start to her bid for a spot in the final four as Pennetta secured two early breaks of serve to claim a 3-0 lead.
Williams responded impressively, and she quickly dismissed any chances of a surprise result with breaks of her own.
The top seed was forced to save two break points at 5-3, but the American held her nerve to convert the advantage into a crucial lead.
Pennetta made it difficult for Williams in the early stages of the second set, although she struggled to capitalise on the rare mistakes from her rival.
The Italian's challenge faded late in the match, and Williams managed to secure the victory with two more breaks of serve on a night when she spent just over an hour on court.
