Jankovic, a 2007 semifinalist, beat Romanian Monica Niculescu 7-6 (7-3), 6-2, and the eighth-seeded Williams defeated Israeli Tzipora Obziler 6-3, 4-6, 6-2.

Williams blew a 4-1 lead in the second set against Obziler, who won five straight games in that set and broke Williams' serve to open the third.

Williams, a six-time major titlist, is the reigning Wimbledon champ. She lost to her younger sister Serena in the 2002 French Open finale.

In other action involving top-16 seeds, No. 10 Swiss Patty Schnyder beat Russian Ekaterina Bychkova 6-3, 6-4 and No. 12 Hungarian Agnes Szavay eliminated Japan's Ayumi Morita 6-1, 4-6, 6-4.