ROME — Top-ranked Serena Williams dispatched Maria Kirilenko 6-1, 6-4 Thursday, then waited to see if she will meet sister Venus in the Italian Open semifinals.

Venus Williams was up against Jelena Jankovic in a night match of former Rome champions at the Foro Italico.

"I have a really tough opponent next match whether it's Venus or Jelena," Serena said. "Obviously, 'Go V!'"

Serena had been out with a left knee injury since winning the Australian Open in January.

"My knee is feeling good so far," she said. "I can't believe I'm still in the tournament — it's weird."

Former No. 1 Ana Ivanovic defeated Nadia Petrova 6-2, 7-5 to reach her first semifinal since losing to Justine Henin in January in Brisbane, Australia.

With her ranking down to No. 58, Ivanovic recently hired Steffi Graf's old coach, Heinz Gunthardt, to improve her game.

"We've worked a lot the last few weeks and I feel great out there," Ivanovic said.

Ivanovic's semifinal opponent will be 26th-ranked Maria Jose Martinez Sanchez of Spain, who beat Lucie Safarova 7-6 (6), 6-4.

After cruising through the first set and taking a 4-0 lead in the second, Serena lost three straight games before regaining control on her service games. She blasted aces at 123 mph and fired baseline winners at will.

Serena had an 8-1 edge in aces and 19-7 in winners. She attributed the brief lapse in the second set to a lack of "match toughness."

"I definitely should have been up 5-0," she said. "Hopefully as I start playing more, I'll start to close these games out better."

Serena won this clay-court warmup for the French Open in 2002 en route to her only title at Roland Garros.

Martinez Sanchez maintained her focus during a brief downpour that interrupted play for 15 minutes just after the start of the first-set tiebreaker. The Spaniard also controlled the play with her big first serve, landing seven aces.