Serbian stars Novak Djokovic and Jelena Jankovic hobbled to victory on centre court while the Russian assault continued on day four of the US Open.

An ailing Djokovic overcame a left foot injury to defeat Arnaud Clement 6-3, 6-3, 6-4 in his opening match, while Jankovic struggled with fatigue but held on to beat Sofia Arvidsson 6-3, 6-7 (5/7), 7-5 in their second round match on Wednesday.

"I had to be consistent and try to get a high percentage of my first serves in," Djokovic said. "I didn't return so well and I had a lot of ups and downs and big frustrations.

"But it is the first match. It is always the trickiest one but hopefully the next one will be better."

Djokovic reached the final in New York last year where he lost to four-time reigning champion Roger Federer and has won three titles this year including his first Grand Slam title at the Australian Open.

The 21-year-old Serbian is also fresh off winning the bronze medal at the Beijing Olympics.

"I played good tennis today, enough to win," Djokovic said.

Djokovic moves through to the second round where he will face American Robert Kendrick.

In the third set against Clement, Djokovic twisted his left ankle while lunging for a shot on the main Arthur Ashe Stadium.

At the time he was two sets up and leading 2-1 in the third. After a 10 minute time out to get the ankle taped, the match resumed with Clement winning the next point to level the final set at 2-2.

But Djokovic cruised from there winning four of the next five games, clinching the win in straight sets when Clement's final shot sailed long.

Djokovic expects the foot to be almost as good as new in a couple of days.

"It is going to be a good two days," Djokovic said of his ankle. "After it happened I was thinking more of it than I was the pain, so it is not really a big deal.

"But in a certain moment I felt big pain, so I had to get it taped."

The 23-year-old Jankovic has reached two semi-finals in Grand Slams this year (French Open and Australian Open) but has never made it to a final in 20 career major appearances.

Jankovic has six career singles titles but just one victory to show for her consistent play this year. The pesky Swede Arvidsson made Jankovic work for Wednesday's win.

"It was really tough. I am completely out of breath," second-seeded Jankovic said immediately after the two-hour, 45-minute match. "I was pushed to the limit."

Jankovic moves through to the third round where she will face China's Zheng Jie who beat Anabel Medina Garrigues of Spain 6-1, 6-4 on Wednesday. Zheng reached the semi-finals at Wimbledon earlier this year.

Jankovic, who has suffered a string of injuries this year, took a couple of tumbles on Wednesday but got through the match unscathed.

Drama queen or tennis warrior -- only Jankovic knows how much of her constant grimacing on the court is real or not.

"I was concerned I was going to get my dress dirty," she said of one of her spills. "That was my biggest concern."

Five Russians, including four seeded players, advanced on Wednesday while Vera Zvonareva became the first seeded Russian casualty.

Beijing Olympic gold medallist Elena Dementieva beat Pauline Parmentier of France 6-2, 6-1. Dementieva, the runner-up in 2004, is making her 10 straight US Open appearance.

"You have to find a way to win," said Dementieva, of Moscow said. "The most important thing is to stay positive in the difficult moments in the match even when you feel tired."

Dementieva, who is ranked sixth in the world, moved through to the third round where she will face Great Britain's Anne Keothavong who surprised 25th seeded Francesca Schiavone 6-2, 3-6, 6-4.

Third-seeded Svetlana Kuznetsova beat 18-year-old Sorana Cirstea 7-6 (7/3), 6-1.

"It was all about the first set," Russia's Kuznetsova said. "When I got into a dangerous situation I started moving her around a little bit more. In the second set I was able to gain more confidence."

Another Russian Olympian Zvonareva was sent crashing out of the event, losing her second round match 6-3, 6-3 to unseeded Tatiana Perebiynis.

Zvonareva was in the same side of the draw as Jankovic and Lindsay Davenport who beat another Russian Alisa Kleybanova 7-5, 6-3 in a night match.

In the other evening match, American eighth seed Andy Roddick defeated Frenchman Fabrice Santoro 6-2, 6-2, 6-2 on the strength of 15 aces.

Russian fifth seed Nikolay Davydenko dispatched Dudi Sela 6-3, 6-3, 6-3 in a men's first round match.

World number ones Rafael Nadal and Ana Ivanovic highlight the schedule on Thursday.

AFP