Djokovic, Kerber aim for semis at US Open

Men's top seed Novak Djokovic and women's No 2 Angelique Kerber look to book berths in the last four of the US Open as the quarterfinals of the year's last grand slam get underway on Tuesday. Kerber, who nearly ended Serena Williams' long run as world No 1 last month in Cincinnati, tries to stay on track for a possible winner-take-all match with the American in the finals when she goes against Roberta Vinci.