Serena Williams and Dinara Safina will fight it out for the Australian Open title and the world No1 ranking after winning their semi-finals today.

Second seed Williams stayed on course for her 10th Grand Slam title with a 6-3, 6-4 win over the in-form Elena Dementieva while third seed Safina beat fellow Russian Vera Zvonareva 6-3, 7-6.

Williams was world No1 for four weeks in 2008 and before the tournament began she said one of her targets this year was to regain that ranking from Jelena Jankovic.

Although she has the chance to do that on Saturday, the American insisted: "Right now, that would be just a bonus. My goal isn't to be No1. My goal is to win one more singles match here. All my hard work is paying off.

"I'm excited that I'm playing really consistently at least making it to the finals of Grand Slams. Safina's playing well and she's going to be tough.

"She obviously wants to win. She's playing amazing and she wants to win a Grand Slam and go for the glory."

Since 2003, Williams has won the Australian Open every two years but the chances of her maintaining that record didn't initially look too promising.

The American had lost her last three clashes against Dementieva, who came into the semi-final unbeaten in 15 matches in 2009.

But Williams said it was her serve that proved the decisive factor today.

"It's so important to serve well against her," she said. "She's a good returner. I moved better and I was definitely more consistent and I kept my cool."

Yesterday she toiled in the searing heat against Svetlana Kuznetsova and only fought back to win after the roof on the Rod Laver Arena was closed. With temperatures in Melbourne hitting 105°F for the second successive day, the roof was closed from the start and Williams looked much more composed.

The match turned in the eighth game when she broke Dementieva to give herself an opportunity to serve for the first set. Williams rattled through the game and sealed the set in 44 minutes when Dementieva's audacious backhand drop shot landed narrowly wide.

The first game of the second set lasted a staggering 14 minutes as Williams fashioned a string of break points only for Dementieva to snatch the advantage back and eventually hold after six deuces. The Russian then broke Williams and raced into a 3-0 lead before the world No2 began another of her characteristic fightbacks.

She held to love, then broke Dementieva in the fifth game, despite suffering a heavy fall when she was wrong-footed by a forehand drive from the Russian, though Williams said it would not be a problem for Saturday.

"I usually don't feel tumbles until like four days later because of the adrenaline. I'll be home on Tuesday, I'll be like, 'Oh, my God, my leg hurts'. I'll realise, 'Oh, that's why'."

Williams then held to level it at 3-3 before neither could hold serve, with Dementieva breaking once while Williams broke twice to give her the opportunity to serve for the match.

She managed two massive aces, the second of which prompted a cry of anguish from Dementieva and set up match point, then sealed victory after she ran the Russian around and smashed an overhand into the open court. The defeated 27-year-old felt she played into Williams's hands.

"I was maybe not aggressive enough and maybe I was playing not deep enough, which allowed her to be very aggressive and dictate the game," said Dementieva.

By contrast, fellow Russian Safina made the most of her opportunities as she took one hour 46 minutes to beat seventh seed Zvonareva.

Safina, who reached the final of the French Open last year before going down to Ana Ivanovic, looked very composed in her first last-four appearance at Melbourne Park and pounded her opponent from the baseline with punishing forehands and ripping backhand ground strokes.

Safina, 22, is thrilled to be given the chance to be the world's top player. "To fight for the No1 spot is unbelievable," said the sister of double Grand Slam champion Marat Safin. "Vera had won so many matches 6-0 whereas I've been struggling, playing three sets.

"But now was the time to play and I was ready for anything."

In the girls' singles Britain's Laura Robson reached the semi-finals after her opponent, No4 seed Elena Bogdan, pulled out with an ankle injury. The 15-year-old fifth seed, who has yet to drop a set in Melbourne, was leading 6-3, 2-5 when the Romanian quit.

Robson will now face top seed, Thailand's Noppawan Lertcheewakarn, who she beat in last year's Wimbledon girls' final. However, Guernsey's ninth seed, Heather Watson, was beaten 6-3, 7-5 by Russian third seed Ksenia Pervak.