World number one Victoria Azarenka has advanced to the third round of the US Open by defeating Belgian qualifier Kirsten Flipkens 6-2 6-2 in only 65 minutes at Arthur Ashe Stadium.
The reigning Australian Open champion, who has reached the last eight in every Grand Slam event except the US Open, will next face the Chinese 28th seed Zheng Jie, who beat Slovakian qualifier Magdalena Rybarikova 6-3 6-1.
The 23-year-old from Belarus, is seeking her 13th career title and fifth trophy of the year on the Flushing Meadows hardcourts.
However, Azarenka could be dethroned from the top ranking by Agnieszka Radwanska or Maria Sharapova if she fails to make the final.
Meanwhile, the Russian 19th seed Nadia Petrova has reached the third round in only 57 minutes with a 6-1 6-1 triumph over Romania's Simona Halep.
Next for Petrova will be either Czech 15th seed Lucie Safarova or Canada's Aleksandra Wozniak.
Three-time US Open champion Kim Clijsters, playing her farewell event, risks her 22-match US Open winning streak against Britain's Laura Robson in another second-round match.