?Ana Ivanovic of Serbia celebrates after defeating Zheng Jie of China during the U.S. Open tennis tournament in New York, September 1, 2010. [Xinhua/Reuters Photo]

Former world number one Ana Ivanovic is trying to recapture her old form, easing past China's number 21 seed Zheng Jie on Wednesday in the US Open second round.

The 22-year-old Serb, who won the French Open in 2008, needed less than an hour to dispatch Zheng 6-3 6-0 in sweltering conditions on Arthur Ashe.

Ivanovic has suffered from a lack of form over the last two seasons but has recently started a gradual climb up the world rankings and was far too strong for former Wimbledon semi-finalist Zheng.

Using her powerful forehand to good effect, Ivanovic raced out into a 5-1 lead in the first set before Zheng briefly hit back with a break of serve of her own.

However, Ivanovic held her nerve and eventually closed out the opening set before going on to completely dominate the second.

It's kind of out of Ivanovic's expectation to go through Zheng in this way. "I was really happy with today's game, because she's tough opponent and I lost to her last couple of times we played. I was expecting really tough match," said the unseeded Serbian.

"Actually conditions a little bit tough out there because it was very gusty. I played and just stayed aggressive. Even when errors crept in, I just kept looking for the ball that I knew I had to hit. It worked out well."

Zheng had struggled with unforced errors throughout the contest and looped a forehand out on match point to hand a comfortable victory to Ivanovic.

Next up is a third round showdown with Virginie Razzano after the Frenchwoman saw off compatriot and number 13 seed Marion Bartoli 7-5, 6-4.