Ivanovic undaunted by Serena challenge

Ana Ivanovic, who rose to No 1 in the world after her 2008 French Open victory, is excited to take on resurgent Serena Williams for a US Open quarterfinal berth as she continues her own climb back to the game's summit.

"It's exciting," said Ivanovic, who advanced to the last 16 with a 6-3, 6-4 victory over American Sloane Stephens.

"I think she's the hottest player out there at the moment. It is going to be a good challenge."