World number one Dinara Safina had to overcome some tough moments before reaching the second round of the China Open ATP/WTA tournament on Sunday.

Russia's Dinara Safina returns a shot to Roberta Vinci from Italy during the China Open women's singles first round in Beijing, Sunday, October 4, 2009. [Xinhua]

American Serena Williams also ensured a booth in the round of 32 after defeating Kaia Kanepi from Estonia 7-5, 6-4 in one hour and 22 minutes.

Serena Williams of the United States returns a shot to Kaia Kanepi of Estonia during the first round match of women's singles at China Open 2009 in Beijing, capital of China, Oct. 4, 2009. Serena Williams won 2-0. [Xinhua]

Williams broke in the eighth game to lead at 5-3 in the opening set but Kanepi, capitalizing on her opponent's double faults, took a break back in the next game.

In the 12th game and leading 6-5 on Kanepi's serve, Williams hit top gear to get three set points and finally converted on the third to take the set at 7-5.

Kanepi showed battling qualities at the start of the next set, storming to a 3-0 lead while Williams, the current world number two, held her nerve to level the match and never looked back before claiming the set at 6-4.

Safina, who is still looking for her first Grand Slam title to underline her credentials, looked a little bit nervous in the match against Roberta Vinci from Italy, committing eight double faults. Fortunately, the 23-year-old had the whole match under her control and won 76 percentage on her first serve.

"In the first set, I think it was only once, I rushed a little bit. And the same exact happened in the second set. I wanted to be more aggressive, but it was a mistake. Overall I think I served well in important moments," said Safina.

The local fans was disappointed by Chinese Zheng Jie's elimination from the opening round but they still gave a standing ovation to the winner Svetlana Kuznetsova, sixth seeded in the competition.

Both players played solid tennis in the opening set, with each being broken once. Kuznetsova was more consistent, winning the tiebreak at 7-3 and going on to win the second set at 7-5.

"I'm not afraid of playing her any more. In the previous meeting, I was always lagging behind and then fought to catch up. Although I lost the game, I did't feel I am in a different league, " said Zheng, who is still nursing her wrist injury.

Denmark's world number five Caroline Wozniacki became the major casualty after losing to Spaniard Martinez Sanchez.

Elena Dementieva of Russia returns a shot to Anna-Lena Groenefeld of Germany during the first round match of women's singles at China Open 2009 in Beijing, capital of China, Oct. 4, 2009. Dementieva won 2-0.[Xinhua]

The two hours and 30 minutes marathon became sort of nightmare for the Denish sensation as the 19-year-old, who made her mark by reaching this year's U.S. Open final, had to battle two tiebreak before being whitewashed in the decider.

Elsewhere, Russia's world number four Elena Dementieva was hardly tested by German Anna-Lena Groenefeld, winning at 6-4, 6-0 while France's Wimbledon semifinalist Marion Bartoli, 14th seeded at the elite tourney, won over Slovakia's Magdalena Rybarikova 6-2, 4-6, 6-3.