Azarenka, ranked No. 1 in the world, stayed perfect in 2012 with a 6-0, 6-4 victory over Yanina Wickmayer. Azarenka won 62 percent of the points both serving and receiving. She dropped just seven points -- two off Wickmayer's serve -- in the first set.
Radwanska earned a semifinals shot at Azarenka with a 6-1, 6-1 win over Christina McHale. Radwanska has six breaks in the seven games McHale served.
Third-seeded Samantha Stosur and No. 5-seeded Marion Bartoli both came out of three-set matches with wins and will meet in the other semifinal.
Stosur topped Monica Niculescu 6-2, 2-6, 6-3 despite losing her serve four times. However, she was good on all five of her break chances over the first and third sets in improving to 3-0 lifetime versus Niculescu.
Bartoli outlasted Lucie Safarova for a 7-5, 4-6, 6-1 win. After the players split the points in the first two sets almost evenly -- 76-75 in Bartoli's favor -- Bartoli lost only nine of the 34 points in the final set.
Azarenka is 7-3 lifetime versus Radwanska, including a pair of three-set wins this year. Bartoli, who won in straight sets both of the last two times she played Stosur, is 3-2 in her career against the 2011 U.S. Open champion.