The Wimbledon runner-up lost a second set tiebreak to Romanian Sorana Cirstea to set up a final set decider.

But the Canadian seventh seed kept her focus to finally dispatch Cirstea 6-2, 6-7(4), 6-4.

"I had to battle in the third," said the 20-year-old after two hours and 17 minutes on court.

"I just believed in myself and told myself to keep fighting.

"I want to play better tennis in the next round but at least I have that chance."

The top seed in the women's singles, American Serena Williams, who is also the defending champion, dropped just a single game in a 6-1, 6-0 win over countrywoman Vania King.

Victoria Azarenka of Belarus, the beaten finalist at Flushing Meadows in the last two years, beat Christina McHale of the United States 6-3, 6-2.

In an all Czech affair, defending Wimbledon champion Petra Kvitova, the third seed, beat Petra Cetkovska 6-4, 6-2

But it was not all plain sailing for the players in the frame to win the final Grand Slam of the year.

Serbian number eight seed Ana Ivanovic lost 7-5, 6-4 against Karolina Pliskova of the Czech Republic.

Ivanovic said afterwards she had "really struggled" to find her rhythm.

Fifteen-year-old teenage sensation CiCi Bellis, who made it into the second round despite being ranked outside the world' top 1,000, went no further after losing to Zarina Diyas of Kazakhstan.

Andy Murrary did not suffer the cramp that unsettled him in his opening match of the US Open ©Don Emmert/AFP/Getty Images



In the men's draw, there was a welcome straight sets win for 2012 US Open champion Andy Murrary.

The Briton had to battle cramp in his first round match, but was untroubled in a 6-3, 6-3, 6-4 win over Matthias Bachinger of Germany.

Top seed Novak Djokovic of Serbia dispatched Frenchman Paul-Henri Mathieu 6-1, 6-3, 6-0, while Canadian fifth seed Milos Raonic won 7-6(4), 5-7, 6-4, 7-6(3) over Peter Gojowczyk of Germany.

Ninth seed Jo-Wilfried Tsonga of France beat Kazakhstan's Aleksandr Nedovyesov 6-3, 6-4, 6-4.

Tomorrow will see men's second seed Roger Federer of Switzerland in second round action, and Russian Maria Sharapova play her third round match against 2013 Wimbledon runner-up Sabine Lisicki of Germany.

Contact the writer of this story at [email protected]