Toiling Jankovic and Kuznetsova secure victories

NEW YORK (Reuters) - Second seed Jelena Jankovic and former champion Svetlana Kuznetsova had to work much harder than expected to shake off their opponents in the second round of the U.S. Open on Wednesday.

Serb Jankovic squandered a match point in the second set before scraping past Swede Sofia Arvidsson 6-3 6-7 7-5 and Russian Kuznetsova overcame a slow start to beat Romanian teenager Sorana Cirstea 7-6 6-1.

Olympic champion Elena Dementieva, however, had no complaints about not playing to her potential after completing a 6-2 6-1 demolition of Pauline Parmentier of France.

Jankovic, who reached the last four at the U.S. Open in 2006, needed two hours and 45 minutes to subdue the 63rd-ranked Arvidsson on the Arthur Ashe Stadium court.

The Serb twice served for the match in the second set and also led 3-0 in the tiebreak before the Swede pegged her back with a series of stinging groundstrokes.

Jankovic had to hold off another Arvidsson comeback in the decider before booking her place in the third round against Wimbledon semi-finalist Zheng Jie.

"It was really tough and I am completely out of breath," Jankovic said in a courtside interview. "I struggled out there and my opponent played really well and pushed me to the limit.

"I am not yet at my full potential, I still have a long way to go to be where I want to be."

RAISED LEVEL

Kuznetsova, who clinched the 2004 title in an all-Russian final with Dementieva, trailed world number 53 Cirstea 4-2 in the opening set before raising the level of her own game.

"In the first set, I was going out there ... but I had no clue how she will play," the third-seeded Russian told reporters after setting up a meeting with Slovenian Katarina Srebotnik.

"She plays the ball really flat and fast so, for me, it was all about this first set. I realized I had to go more to the forehand because (on her) backhand she was making good shots."

Asked if she was happy with her game, Kuznetsova replied: "No, not really. But I don't think you should be... playing your best game in the first (rounds).

"I'm not in my best shape now and I haven't been playing well before the U.S. Open. But grand slams kind of keep me much more motivated and I do much more better in grand slams."

Fifth-seeded Russian Nikolay Davydenko charged into the second round of the men's event with a comfortable 6-3 6-3 6-3 win over Israel's Dudi Sela.

The Russian has not won back-to-back matches since winning a low-key claycourt tournament in Warsaw in June but appeared to have regained his form to dispatch Sela.

American favorites Lindsay Davenport and Andy Roddick will take centre stage in Wednesday's night session in the Arthur Ashe Stadium.

Former world number one Davenport faces Russian Alisa Kleybanova before big-serving Roddick, the 2003 champion, takes on Frenchman Fabrice Santoro.

(Editing by Pritha Sarkar)