- World No. 1 and No. 3 both assured of place at lucrative $4.9 million season finale
- Azarenka and Sharapova meet in Friday's U.S. Open semifinal in New York
- Italy doubles pairing Sara Errani and Roberta Vinci also assured of attending Istanbul event
- Top eight women's singles players and top four doubles pairings will take part
World No. 1 Victoria Azarenka and third-ranked Maria Sharapova have become the first players to qualify for the season-ending WTA Championships in Turkey, the women's tennis tour announced Thursday.
The annual tournament is being hosted at Istanbul's Sinan Erdem Dome for the second time, with the top eight singles players and the four highest-ranked doubles teams battling for a share of the $4.9 million prize pot.
Before the U.S. Open started last week, Sharapova led the WTA Championships points standings ahead of Azarenka and second-ranked Wimbledon finalist Agnieszka Radwanska, who suffered a surprise fourth-round defeat in New York.
"Last year, the atmosphere in Istanbul was great and I am looking forward to playing there again," Azarenka said in a WTA statement.
The 22-year-old will be looking to go one better than in 2011, when she lost to the Czech Republic's Petra Kvitova in the final, and cap an amazing 12 months.
The Belorussian assumed the top spot in the women's rankings for the first time in January after beating Sharapova in the Australian Open final.
It was part of a winning streak which lasted 26 matches as she won four titles including victories in Doha (beating Australia's 2011 U.S. Open champion Samantha Stosur in the final) and Indian Wells, where she again overcame Sharapova.
Winning the prestigious event would also cap a momentous year for the Russian, who completed a career grand slam by winning the French Open in June and briefly regained the No. 1 ranking for the fifth time in her career.
"It will be a great finish to the season in Turkey. We received such incredible support from the fans last year, so I'm looking forward to competing against the world's best players again," the world No. 3 said in a WTA statement.
Sharapova had reportedly planned to get married in Istanbul in November, but the 25-year-old said after her third-round win in New York last week that she is no longer engaged to Turkey-based former NBA star Sasha Vujacic.
"It was a really nice period of time for both of us, but, you know, our career schedules just made it extremely difficult to see each other with the traveling," she told reporters.
Sharapova will again face Azarenka on Friday when they battle for a place in the U.S. Open final. The winner will face either Italy's Sara Errani or Wimbledon and Olympic champion Serena Williams the following day.
Errani has also qualified for the Istanbul tournament, which starts on October 23, booking a place in the doubles competition with her playing partner and compatriot Roberta Vinci.
Errani and Vinci will assume the No. 1 and No. 2 doubles ranking spots when the new list is published after the U.S. Open on Monday.
Since teaming up on a regular basis in 2010, the pair have bagged 12 doubles titles. They won the French Open in June after losing in the Australian Open final, and were due to play in the semifinals of the U.S. Open on Thursday.