Maria Sharapova overcame a first-set blip to reach the second round of the US Open.

The 2006 champion had to fight hard before overcoming Jarmila Groth 4-6 6-3 6-1 at the Arthur Ashe Stadium.

Error-strewn Jelena Jankovic had to draw on all her resources as she squeezed into the second round of the US Open 6-4 4-6 7-5 against Simona Halep.

Fourth seed Jankovic took an opening set containing seven breaks of serve, but her 18-year-old Romanian opponent took the tie into a decider by squaring the match by the same scoreline with an ace.

Halep’s big forehand helped her to serve for the match at 5-4, but Jankovic rallied to square the match at 5-5 as her rival ran out of steam.

The Serb then took the next two games to set up a clash with Croatian Mirjana Lucic, who defeated Alicia Molik in straight sets.

Jankovic revealed afterwards she had not initially realised the severity of the situation.

“I was in some sort of zone, I thought it was 4-3 and then thought, ‘Oh my God’,” she said. “It was unbelievable, I’m so happy to get through.

“First-round matches are never easy and today was really hard. It wasn’t my best game, so I had to work hard to get through. It’s really hot out there, I don’t know how many degrees but it’s really hot, especially on one side (of the court) with the sun in my face.

It took until 4:45pm local time on the second day for the first female seed to lose, China’s Li Na going down in three sets to Kateryna Bondarenko.

Li, who reached the semi-finals of the Australian Open earlier this year and was seeded eighth here, won the first set 6-2 but Ukrainian Bondarenko hit back to win the next two 6-4 6-2.

Eleventh seed Svetlana Kuznetsova was also made to fight all the way as she edged out veteran Kimiko Date Krumm, the oldest woman in the draw.

Kuznetsova, the 2006 champion, took nearly two hours to beat the 39-year-old Japanese 6-2 4-6 6-1 and set up a clash with Anastasija Sevastova.

The Latvian was leading 6-2 2-0 against Regina Kulokova when her Russian opponent retired.

Lucie Safarova, the 26th seed, took the opening set against Tamira Paszek, but the world number 198 from Austria fought back for a 2-6 7-5 6-2 victory.

However, the Polish Radwanska sisters enjoyed comfortable passages into the second round.

Ninth seed Agnieszka, a second-round casualty last year, took four of her five break opportunities to record a 6-4 6-3 win against Arantxa Parra Santonja.

Agnieszka’s younger sister Urszula ousted former world number five Anna Chakvetadze 6-3 6-3.

Rounding out the action on Day Two was top seed Caroline Wozniacki who progressed into the second round of the US Open with a 6-1 6-1 victory over American wild card Chelsey Gullickson.