Top seed Ana Ivanovic struggled but held for the win in her opening match while a pair of wannabe number ones advanced in straights sets during day two of the US Open.

World No 1 Ivanovic, who captured the French Open earlier this year for her first Grand Slam title, didn't make the opening statement she had planned on Tuesday.

The 20-year-old Serbian survived a scare from Vera Dushevina before winning 6-1, 4-6, 6-4 at the Billie Jean King National Tennis Centre.

"Obviously my lack of practice showed off a little. This match is going to help me because it was so challenging. I was missing a lot of match practice so I got a tough one," Ivanovic said.

In contrast, Olympic silver medallist Dinara Safina and Serena Williams won their first round matches in straight sets on Tuesday.

Both have a chance at supplanting Ivanovic as the top ranked WTA player if they reach the finals in the $20.6 million event.

Safina, who is trying to put a fitting exclamation point on a superb season, defeated Kristie Ahn 6-3, 6-4. The 22-year-old Safina, has won three titles in 2008 but hasn't made it past the quarter-finals in the US Open.

Two-time champion Serena Williams rolled to an easy win by beating Kateryna Bondarenko 6-1, 6-4.

The 26-year-old American continued her solid play on hardcourts by firing six aces en route to a victory in just 56 minutes.

The women's draw is wide open this year as the last three champions (Maria Sharapova, Kim Clijsters, Justine Henin) are all absent.

Ivanovic had to overcome some anxious moments in the third set as she double faulted on her first match point before clinching the victory on her second match point.

She finished with three double faults and 40 unforced errors but played better on the big points than her Russian opponent, converting four of eight break point chances.

"The last game I had a couple of mishits but I tried to stay strong, concentrate on each point and forget what happened. I am so happy I managed to do that," Ivanovic said.

She moves through the second round where she will face Julie Coin of France who beat Australian Casey Dellacqua 7-6 (8/6), 7-6 (7/4).

Safina hammered five aces and fired 20 winners to just eight for American qualifier Ahn in the one hour, 24 minute match.

Safina had to work harder than expected for the victory as Ahn posted less unforced errors (21-35) and had just one double fault.

"It was a little bit windy outside so I am happy I could play two sets and win my match. Actually she (Ahn) is a very good player," Safina said.

It would be a windfall victory for Safina if she breaks through and wins the US Open.

She placed first the US Open Series leading up to the final Grand Slam of the season, which means she would receive a one million dollar bonus in addition to the $1.5 million in first place prize money.

She advances to the second round where she will face Taiwan's Chan Yung-jan who beat Stephanie Cohen-Aloro of France 4-6, 7-5, 6-3.

On the men's side of the draw, ranked players Fernando Gonzalez, Fernando Verdasco, Tommy Robredo, Ivo Karlovic and Igor Andreev all won their opening matches.