Serbia\'s Ana Ivanovic reached the US Open third round on Thursday, but admitted she needs to take painkillers every morning to see her through the season\'s last Grand Slam tournament. The 12th-seeded Serb, who has never got beyond the fourth round in New York, made the last 32 with a 6-2, 6-2 win over Sofia Arvidsson of Sweden. But the 2008 French Open champion is still bothered by a right foot injury which forced her out of the Cincinnati tournament on the eve of the US Open. \"I still have to take a handful of pills every morning,\" said the 24-year-old. \"It was a little bit unfortunate but it\'s part of the sport. We play so much and changing surfaces and continents. My foot has been healing and at the moment I am feeling healthy.\" Ivanovic goes on to face either America\'s Sloane Stephens or German qualifier Tatjana Malek for a place in the last 16. Fellow Serb Jelena Jankovic, seeded 30th and the 2008 runner-up, also made the third round with a 6-4, 6-2 win over Spain\'s Lara Arruabarrena-Vecino. She next meets either second seed Agnieszka Radwanska of Poland, the Wimbledon runner-up, or Spain\'s Carla Suarez Navarro. Russian 14th seed Maria Kirilenko, watched by ice hockey superstar boy friend Alex Ovechkin, saw off Hungarian 33-year-old Greta Arn 6-3, 6-2. Slovakian 13th seed Dominika Cibulkova, a quarter-finalist in 2010, edged Serbia\'s Bojana Jovanovski 7-6 (7/3), 7-6 (7/3). Later Thursday, five-time champion Roger Federer, bidding to become the first six-time US winner in the Open era, tackles 32-year-old German Bjorn Phau. The two first met in 1999 in Washington, which was the first North American hardcourt event for either man -- and Phau won in straight sets. Federer won both their subsequent meetings, at the 2007 Australian Open and at the 2010 Estoril claycourt tournament. World number one Federer is playing in his 52nd straight Grand Slam event while Phau, the world 83, has never got beyond the second round of a major. Both Williams sisters also take to the court looking to reach the third round. Three-time champion Serena, who suffered an ankle injury scare playing doubles on Wednesday, goes for her 60th career win at the tournament when she tackles Spain\'s Maria Jose Martinez Sanchez. That could be a spicy affair after Williams accused the Spaniard of cheating when they clashed in the 2009 French Open. Two-time champion Venus faces sixth seed, and 2011 semi-finalist, Angelique Kerber, just a month after the German knocked her out of the Olympics. Kerber has won a tour-leading 54 matches in 2012 and also ended Serena Williams\' 19-match win streak with victory in the Cincinnati quarter-finals.