NEW YORK  - Polish second seed and Wimbledon runner-up Agnieszka Radwanska matched her best US Open performance on Saturday by reaching the fourth round with a 6-3, 7-5 win over error-plagued Jelena Jankovic.

Radwanska recorded her 51st victory of the year as she and the 30th-ranked Serb, a former world number one and 2008 finalist, toiled in 32-degree Celsius heat.

Vinci reached the last 16 for the first time with a 6-2, 7-5 win over Slovakia's 13th seed Dominika Cibulkova, and a quarter-finalist in 2010.

Radwanska triumphed in a gruelling 98-minute contest which featured 10 breaks of serve, with Jankovic finally undone by her 37 unforced errors, the last of which came on match point with a wild, ballooned forehand.

Radwanska again played with heavy strapping on her right shoulder but insisted she was not hurt. Vinci equalled her best Grand Slam performance with a fourth successive victory over Cibulkova and third this year after previous wins in Indian Wells and Madrid.

Former champions Roger Federer and Serena Williams complete the afternoon session on Arthur Ashe Stadium.

Top seed Federer, bidding to become the first man in 87 years to win six US Open titles, faces Spanish 25th seed Fernando Verdasco, a player he has beaten in all four previous meetings.

Fourth-seeded American Williams, the champion in 1999, 2002 and 2008, tackles Russia's Ekaterina Makarova who knocked her out of the Australian Open in the fourth round earlier this year. Britain's Olympic champion Andy Murray, the third seed, defends a 6-0 career record against Spain's Feliciano Lopez. The two played at the US Open last year with Murray winning in straight sets.

Milos Raonic, the 15th seed, faces James Blake of the United States trying to become the first Canadian to reach the last 16 of a major for 24 years.

Blake, the world 114, is one of four wildcards who has made it to the third round, the most at any Grand Slam in the Open era.

Defending champions Novak Djokovic and Samantha Stosur advanced in straight sets while British teen Laura Robson sent Li Na home after sending Kim Clijsters into retirement.

Russian third seed Maria Sharapova, the 2006 US Open champion, and Argentine seventh seed Juan Martin Del Potro, the 2009 US Open winner, were also among those moving on during the fifth day of the year's last Grand Slam tournament.

Serbian second seed Djokovic overwhelmed Brazil's Rogerio Dutra Silva 6-2, 6-1, 6-2, never facing a break point and winning 90 percent of his first-serve points to reach the last 32 in 99 minutes on the Flushing Meadows hardcourts.

Robson, the youngest player in the world top 100 at 89th, became the first British woman in the fourth round of a Grand Slam since Sam Smith at Wimbledon in 1998 and the first in the Open's last 16 since Jo Durie in 1991.

Li did not reach the last eight at any Grand Slam tournament for the first season since 2008. Stosur, who has not won a title since lifting the US Open trophy last year, took a 7-6 (7/5), 6-2 victory over US 31st seed Varvara Lepchenko and looked forward to the challenge Robson presents.

Sharapova, who completed a career Grand Slam by winning the French Open title in June, eliminated 252nd-ranked US collegian Mallory Burdette 6-1, 6-1. "I'm really happy to go one round further than last year," the Russian beauty said. Next up for Sharapova is a fourth-round meeting with 19th-seeded compatriot Nadia Petrova.

Spanish fourth seed David Ferrer moved into the third round by ousting Dutch qualifier Igor Sijsling 6-2, 6-3, 7-6 (14/12).

Ferrer, a 2007 US Open semi-finalist in his best Grand Slam run, battled to his sixth match point before Sijsling netted a forehand to finally fall.

Czech fifth seed Petra Kvitova ousted Pauline Parmentier 6-4, 6-4 to reach a round-of-16 match against her third consecutive French foe, 11th seed Marion Bartoli, who downed compatriot Kristina Mladenovic 6-2, 6-4.